A Comprehensive Review with Future Prospects on the Medicinal Properties and Biological Activities of Curcuma caesia Roxb.

Plants are the primary source of the food chain and are rich in nutrients and biochemical compounds that mainly give beneficial effects to humans as well as other living organisms. Curcuma caesia Roxb. is a family member of Zingiberaceae commonly known as black turmeric. The leaves and rhizomes of this plant are extensively used in Ayurvedic medicine and as traditional remedies for various ailments. The aromatic rhizomes and leaves are due to the presence of essential oils reported as camphor, ar-turmerone, (Z)-β-ocimene, ar-curcumene, 1,8-cineole, β-elemene, borneol, bornyl acetate, tropolone, ledol, β-elemenone, and α-bulnesene. Previous research studies have revealed most of the biological activities of C. caesia, such as antioxidant, antimicrobial, and anti-inflammatory properties, which are due to the presence of various bioactive components. The diverse chemical composition contained in this plant contributes to various biological activities, which may be beneficial for the health, food, and cosmetic industries. The purpose of this review was to summarise updated research on the in vitro and in vivo activities of C. caesia as well as the current clinical investigations. A compilation of the latest findings regarding the potential activities of C. caesia and mechanisms related to its health benefits is discussed and reviewed. This valuable information is the key that can be used for the development of drugs, functional food ingredients, and food products.


Introduction
Plants are the main source of natural products, which have been used for more than thousands of years for various purposes, including foods, traditional remedies, and ritual activities. Specialized metabolites produced by plants as natural defence mechanisms against diseases, infections, and predators have shown potential to be exploited for the development of new drugs. According to the World Health Organization (WHO), over 80% of the world's population uses herbal and natural products as medicinal treatment [1].
Besides, plenty of research fndings revealed the benefcial therapeutic efects of various herbal plants and their extracts [2]. Te use of herbal plants has gained interest from many sectors and in combating diseases because of their safety, availability, and low cost [3,4].
Te use of modern synthetic drugs has detrimental effects on the liver and/or kidney for long-term use, besides some having uncomfortable side efects. Turmeric is one of the ancient herbs that serves as a spice and possesses pharmacologic efects that have been proven in in vitro and in vivo studies. Urbanisation changed the lifestyle of people, which leads to increasing cases of numerous diseases. Various studies have been performed on the therapeutic properties of Curcuma species, and the ones mentioned here are merely a representation of them. Curcuma caesia contains benefcial components that can be exploited as natural complementary and alternative therapies to drugs for combating diseases, especially in humans. Table 1 shows the classifcation of C. caesia according to the data from the Global Biodiversity Information Facility [5]. Curcuma (Zingiberaceae) consists of more than 80 species of rhizomatous herbs that are mostly native to tropical South Asia. Among the Curcuma genus, C. caesia is still considered an underutilised species, which has not been widely studied or commercially exploited yet. C. caesia is a perennial rhizomatous plant that erectly grows to a height of 0.5-1.0 m. It has a large tuberous rhizome, broad, vertical oblong leaves, and a pale yellow with reddish border fower [6]. Te inner part of the rhizome is bluish-black or buf in colour and has a circular arrangement that is frequently misunderstood as the growth ring [7]. Figure 1 shows the rhizome (a), transverse cut of rhizomes (b), fower (c), and whole plant of C. caesia (d).
C. caesia, known as kali haldi (Hindi), black turmeric (English), and kunyit hitam (Malaysia), grows in humid, rich, and clayey soils. It originated throughout the Himalayan region, such as India and South East Asia. Even though there is no reliable report on the use of this plant as food material, its rhizome has been vastly reported to be used as a remedy in treating wounds, leprosy, bruises, toothache, snake and scorpion bites, ulcer, leucoderma, asthma, piles, bronchitis, and others [7]. Te leaves were also found to be benefcial as rice seed germination stimulants, while the dried leaves can act as a fuel source [8]. Tis plant is currently considered an endangered species, which prompts the initiative of researchers to invent new approaches, such as plant cells and tissue culture in order to conserve the species from extinction [9]. Tis plant is considered an endangered species due to its traditional human usage, low multiplication rate in the soil, and root susceptibility to disease caused by the parasitic fungi, Pythium species [10]. Tus, this review was intended to summarise the most recent research on the in vitro and in vivo activities of C. caesia as well as the most recent clinical studies.

Traditional Uses
C. caesia has been used for a long time as a traditional herb in the Ayurvedic, Unani, and Siddha herbal systems [11]. Figure 2 summarises the overall information about C. caesia. Each part of the plant, especially the rhizomes and leaves, contained a diferent distribution of chemical constituents, which are used medicinally to combat various illnesses. Besides, C. caesia is also used in folk cosmetics and traditional medicine. Various parts of this plant are used for diferent purposes. In Kota Belud, Sabah (Malaysia), young leaves of C. caesia are often consumed raw as salad (ulam) by the Sama-Bajau people. Te leaves are freshly eaten or given as a drink to treat cough [12].
Te usage of this plant is more focused on the rhizome part. Te presence of chemical compounds makes it aromatic and able to act as a stimulant and carminative agent. Te rhizomes are employed as rubefacients by the "Turkomans" to rub their bodies after Turkish baths. In its fresh state, it is used as a turmeric replacement in Bengal, India [13]. Fresh rhizome is crunched and used as paste for sprains and bruises as well as migraine reliever [14]. Rhizome paste is also used to treat snake or scorpion bites. Powdered C. caesia rhizome is applied by tribal women as a facial mask during their engagement and marriage ceremonies [6]. In addition, it is mixed with honey or milk to be taken twice daily for longevity, weakness, infertility, and irregular menstrual fow [15]. It is also orally administered with water for bloating and stomach ache [14], while an extract prepared from dried rhizomes is taken orally for asthma relief [13].
Other uses of this plant are reported for the treatment of bronchitis, cold, cancer, epilepsy, fever, wounds, leucoderma, pneumonia, piles, tumor, toothache, vomiting, and gout [6,[14][15][16]. Nevertheless, despite its uses in humans, C. caesia is also used in animal healthcare, where rhizome juice is mixed with mustard oil and given to cattle with dysentery once daily on an empty stomach for 2-3 days [16]. Various studies have been conducted on this plant to investigate the scientifc basis for its traditional usage, especially in disease therapies. Figure 2 and Table 2 display the previous fndings of the biological activities by C. caesia.

Phytochemical and Bioactive Constituents
Te colour, odour, and taste of plants are contributed by the specialized metabolites that serve as the plant defence mechanism against adverse conditions caused by pathogens, herbivory, and environmental stress [43]. Te presence of various phytochemicals in plants contributes to their pharmacological activities. Te biological efects of Curcuma species are mainly attributed to the compound known as curcuminoids. Tere are many published articles reporting the presence of specialized metabolites, such as curcuminoids in turmeric, which are mainly accumulated on the rhizomes. Curcuminoids are commonly used as spices, pigments (dye substances), and additives, as well as therapeutic agents [44]. It is a type of fat soluble composed of polyphenolic pigments, the main component of which is curcumin. Beside curcumin, there are other components in the curcuminoids group, which are desmethoxycurcumin, bisdemetoxycurcumin, and cyclic curcumin. Among these, curcumin is the major component, and cyclic curcumin is     Tomas and Jose [31] Evidence-Based Complementary and Alternative Medicine 5 Rhizome, leaves, stem Soxhlet extraction with water, methanol, acetone, and chloroform Antibacterial activity Te rhizome extracts were found to be more efective in inhibiting the bacterial growth as compared to stem and leaf. Methanol and chloroform extracts showed highest activity index against B. cereus (0.55) and K. pneumoniae (0.59), respectively Pandey and Gupta [40] 6 Evidence-Based Complementary and Alternative Medicine Borah et al. [42] Evidence-Based Complementary and Alternative Medicine the minor component [45]. Curcuminoids are also known as diferuloylmethane, which can be found mainly in the rhizome of C. longa and in other Curcuma species. It is insoluble in water and soluble in acetic acid, alkalis, chloroform, ethanol, and ketone [44,46]. In a previous study, the presence of curcumin in the ethanolic extract of C. caesia (8 mg/100 g) by Soxhlet extraction method was the lowest among the other fve Curcuma species: C. longa (125 mg/100 g), C. zedoaria (88 mg/ 100 g), C. angustifolia (71 mg/100 g), C. leucorrhiza (5 mg/ 100 g), and C. amada (11 mg/100 g) [47]. An earlier comparative study [47] on thin layer chromatographic (TLC) profling of two Curcuma species, C. longa and C. caesia, showed the presence of curcuminoids in the rhizomes of both Curcuma species. However, only leaves methanolic extract of C. longa showed distinct bands for curcuminoids. In C. caesia, only curcumin was detected, whereas desmethoxycurcumin and bisdemetoxycurcumin were absent. Abundance of research have been conducted and showed the biological efects of curcuminoids, including antioxidant [48], antitumor [49], anti-infammatory [50], and neuroprotective efects [51].

Evidence-Based Complementary and Alternative Medicine
C. caesia was reported to be rich with major constituents of carbohydrates, proteins, amino acids, steroids, glycosides, favonoids, alkaloids, tannins, and phenols [6,11,[52][53][54][55]. Furthermore, this plant contains essential oils with camphor, ar-turmerone, (Z)-β-ocimene, and ar-curcumene as major compounds (higher than 5%), which produce the aromatic, hot, bitter taste, and pungent smell [56]. Tese metabolites are believed to contribute to the various biological activities of C. caesia. Te diferences in type and quantity of extracted compounds may be due to factors in the plant sample or extraction techniques, including plant sample preparation, type and polarity of solvent, temperature, pH, particle size, pressure, and time, as well as the origin of the plant [57][58][59]. Te phytochemical constituents of C. caesia extracted from rhizomes and leaves using diferent types of extraction methodologies are summarized in the supporting information (Table S1 and Figure S1).

Antioxidant Properties
Te therapeutic efects of some plant parts, such as fruits, vegetables, and grains, which are traditionally used in folk medicine, are usually attributed to their antioxidant compounds [60]. Te protective role of plant phytochemicals may be associated with their antioxidant activity, as they combat oxidative stress in the body by maintaining a balance between oxidants (reactive oxygen species and reactive nitrogen species) and antioxidants [61]. Hence, the antioxidant compounds from natural products constitute the major source of human health promotion and maintenance [62]. In vitro and in vivo studies conducted on C. caesia extracts discovered their antioxidant activity.
Tere were various antioxidant assays tested on C. caesia, such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing activity (FRAP), total antioxidant capacity, thiobarbituric acid reactive species (TBARS) assay, and total phenolic content (TPC). Tese diferent assays measure diferent antioxidant mechanisms; for example, the DPPH assay detects the scavenging activity by donating an electron (primary antioxidant), whereas the FRAP assay determines the ability to reduce ferric to ferrous by donating an electron (primary and secondary antioxidant) [63,64]. Secondary metabolite content in plants is claimed to be the reason for the efectiveness of the plants as herbal medicine. According to Zayapor et al. [65], dietary antioxidants are majorly attributed to phenolic compounds. Te amount of polyphenol and antioxidant ability of each Curcuma species varies; however, previous reports revealed yellow turmeric (C. longa) has higher phenolic content and exhibits stronger antioxidant activity, followed by white (C. zedoaria) and black turmeric (C. caesia) [66,67]. Conversely, protein extracts from C. caesia rhizomes were reported to exhibit higher antioxidant activity by showing the lowest inhibition concentration (IC 50 value) in the DPPH assay compared to C. zedoaria [68].
Te type of solvent used for plant extraction plays an important role by afecting the extraction efciency of the target compounds and infuencing the activities of the extracts [69][70][71]. A study demonstrated that diferent polarities of solvents (hexane, petroleum ether, benzene, chloroform, ethyl acetate, methanol, and water) had signifcant efects on the total phenolic contents, extracted components, and antioxidant activities of fresh and dried C. caesia rhizomes [41]. Te study reported chloroform and benzene extracts contained the highest TPC, with values ranging from 56.64-109.41 mg GAE/g extract. In addition, chloroform extract was revealed to be the most efective extract among the rest as free radical scavengers (DPPH assay), electrondonating agents (ferric reducing activity), and reducing molybdate ions (total antioxidant capacity). Starch isolated from C. caesia rhizomes through a cellulase-assisted method was reported to contain 4.1 mg ferulic acid equivalent (FAE)/ g starch of total phenolic compounds, with only 0.015 mg/g starch curcumin content [30]. Besides, curcuminoid 8 Evidence-Based Complementary and Alternative Medicine pigment (oleoresin) from C. caesia starch also showed antioxidant property by successfully scavenging 14.7% of free radicals in the DPPH assay [30]. Te antioxidant property of this herb was also detected through in vivo studies. A report by Majumder et al. [17] revealed the antioxidant efectiveness of a methanolic extract of C. caesia rhizome by successfully scavenging free radicals in streptozotocin (STZ)-induced diabetes in Wistar rats. Lipid peroxidation was inhibited in diabetic rats treated with methanolic C. caesia extract by the reduction of TBARS level towards normal. Inhibition of lipid peroxidation helps in preventing tissue injury and failure of the endogenous antioxidant defence mechanisms. Besides, gradual healing was seen in the beta cells (pancreas) of the treated rats after treatment with methanolic C. caesia extracts.

Antibacterial Properties.
In some countries, bacterial infection is an epidemic. Exploring the antibacterial efect of Curcuma species has been conducted for many years by researchers, including on Gram-positive and Gram-negative bacteria. Te most common bacteria used in the studies were Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Among them, E. coli was the most resistant strain [72,73].
C. caesia leaves extracted with 50% methanol showed a positive antibacterial efect after 4 to 8 hr of incubation with Bacillus cereus, Diplococcus pneumoniae, Streptococcus pyrogens, and Micrococcus glutamicum [29]. C. caesia was revealed to have antibacterial properties by acetone extract, which showed maximum activity against S. aureus, while chloroform extract showed maximum inhibitory action against Serratia marcescens [31]. Research by Pandey and Gupta [40] reported that the rhizome extracts (chloroform, acetone, and methanol) of C. caesia were found to be more efective in inhibiting the bacterial growth as compared to stem and leaf extracts, excluding aqueous extract. Te rhizome extracts of the plant showed inhibition against Bacillus cereus, B. subtilis, S. aureus, Staphylococcus epidermidis, E. coli, Proteus vulgaris, and Klebsiella pneumoniae. Meanwhile, in other fndings by Borah et al. [42], essential oils from C. caesia leaves displayed an antibacterial efect against B. subtilis, B. cereus, S. aureus, and Salmonella typhimurium, with the lowest minimum inhibitory concentration (MIC) observed against S. aureus by 2.5 μL.
C. caesia was found to exhibit signifcant in vitro antituberculosis activity [32]. An ethanolic extract of C. caesia rhizome was revealed have an efective antimycobacterial activity against Mycobacterium tuberculosis (Mtb H37Rv) and six multidrug-resistant (MDR) clinical strains of Mtb isolated from sputum samples of pulmonary tuberculosis (TB) patients with MIC of 31.25-125 μg/mL. Te same author also reported in vitro cytotoxicity of the extract in human THP-1 macrophages with IC 50 value of 500 μg/mL and 4-16 selective index range.

Antifungal Properties.
Afatoxin is a toxin produced by certain kinds of fungi (moulds) that are found naturally all over the world; they can contaminate food crops and cause serious health threats to humans and livestock [74]. Curcuma extract has been reported to be rich in bioactive compounds, which can act as antifungal agents [11,14,75]. Te rhizome part of C. caesia was reported to have antifungal activity. Essential oil from C. caesia rhizome was tested against a number of human and plant pathogenic fungal strain. An ethanolic extract of C. caesia rhizome was detected to be efective in inhibiting the growth of Aspergillus favus [34]. Other study discovered the antifungal activity by the isolated terpenoid (Z)-7-methoxy-1, 5-dihydrobenzo[c] oxepine from ethanolic C. caesia extract against Fusarium oxysporum, Botrytis cinerea, and Rhizopus oryzae [35]. Diethyl ether fraction of an extract mixture of C. caesia and Ixora coccinea showed better antifungal potential against Botrytis cinerea compared to any extract alone [33]. Nevertheless, a study by Borah et al. [42] on the C. caesia leaf essential oil also found it to have an antifungal efect against Aspergillus fumigatus, Aspergillus niger, Saccharomyces cerevisiae, and Candida albicans.

Antiproliferative and Anticancer Properties
Cancer is one of the major causes of death worldwide and may be developed due to several factors such as an unhealthy diet, genetic predisposition, or environmental factor. Most of the cases are caused by individual lifestyles and take about 20-30 years to develop [76]. Te variety of biologically active components in natural substances, especially plants, were proven to have anticancer properties. Te mechanism of action is through suppressing the infammatory processes that lead to transformation, hyperproliferation, and the initiation of carcinogenesis [77]. Teir inhibitory efects may eventually suppress the fnal steps of carcinogenesis: angiogenesis and metastasis [78].
Methanolic extract of C. caesia rhizomes showed positive efect of anticancer against Ehrlich's ascites carcinoma (EAC) in mice by signifcantly reducing the tumor volume, tumor weight, viable cell count and increasing the lifespan percentage (57.14 and 88.09%) of EAC-treated mice [36]. Te antitumor activity may be infuenced by the cytotoxic efect and antioxidant property of the extract tested. It was assumed that the viability of EAC cells decreased as the oxidative stress in diferent tissues in EAC-bearing mice was reduced. Research on the anticancer efect of C. caesia rhizomes exposed the efectiveness of C. caesia extract against the hepatocarcinogen, diethylnitrosamine (DEN), by enhancing antioxidant status through free radical scavenging mechanisms resulting in attenuation of hepatic enzymes in the serum (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and cancer marker enzyme acetylcholine esterase (AChE)) [37]. Te activities of the antioxidant defence system such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were signifcantly increased in extract-treated mice when compared to controls.
Besides having anticancer property, C. caesia also has the potential to be used as a supplement for cancer treatment with a chemotherapeutic drug (cyclophosphamide) due to Evidence-Based Complementary and Alternative Medicine its capability to prevent drug toxicity through the alleviation of micronuclei formation and to prevent hepatotoxicity and nephrotoxicity caused by the drug [38]. Te latest fnding [39] revealed that hexane rhizome extract of C. caesia exhibited remarkable antioxidant activity with 1200 mg ascorbic acid equivalent/100 g. Te extract was also able to inhibit HepG2 (human liver carcinoma cells) cell proliferation with very low IC 50 value (IC 50 : 0.97 μg/mL), high selective index, and induce cell arrest at the S and G2/M cell cycle phases along with caspase-3-mediated apoptosis.

Anti-Inflammatory and Antiulcer Properties
Infammation is a biological response of the immune system that can be triggered by various factors, which may induce acute and/or chronic infammatory responses in the body systems and organs, potentially leading to tissue damage or disease [79]. One important key role in the process of infammatory is played by prostaglandins [27,80]. Infammatory disease can be reduced or delayed by inhibition of cyclooxygenase (COX) enzymes associated with infammatory intermediates such as prostaglandin and thromboxanes [27]. Anti-infammatory activity of hexane, methanolic, and pure isolate compounds from extract of C. caesia has been positively shown by selective inhibition of COX-2 and slight inhibition activity against COX-1 [68] and is summarized in supporting information (Figure 3). An in vivo study of methanolic C. caesia extract also showed its efectiveness as an anti-infammatory agent, whereby at doses of 200 and 400 mg/kg, it signifcantly reduced the paw edema volume in carrageenan-induced paw edema in rats. Te extract also demonstrated anti-infammatory activity in a cotton pellet-induced granuloma model (subacute) by reducing the dry weight of granuloma [19]. Besides that, anti-infammatory action also can be examined through the egg albumin denaturation assay. A study conducted by Borah et al. [42] discovered that at a concentration of 300 μg/ mL, C. caesia leaf essential oil exhibited the highest albumin denaturation inhibition activity and had lower IC 50 value (182.5 μg/mL) compared to the standard sodium diclofenac (906.5 μg/mL).
Meanwhile, ulcer is a condition of an infammation breakout in the skin or the alimentary tract mucus membrane lining. Production of free radicals, decline of mucosal defensive factor, or internal injuries are among the factors that contribute for the ulceration to take place [81,82]. Various other herbal plants have been reported to possess antiulcer activity, including Euphorbia umbellate (leitosinha) stem bark [83], Osyris quadripartita leaves [84], Filipendula ulmaria (L.) Maxim, and Filipendula vulgaris Moench fower [85]. Previous literature claim that the bioactive components in herbal plants such as favonoids, saponin, tannins gums, and mucilages are possible gastroprotective agents [86].
Efciency of favonoids and tannins as antiulceronic substances among the cytoprotective active materials has been extensively confrmed, whereas other components with other possible mechanisms such as alkaloid can inhibit stress-induced ulcer, and tannins may inhibit ulcer development due to their protein precipitating and vasoconstriction efects, which the astringent action can help precipitating microproteins on the ulcer site, thereby forming an impervious layer over the lining that hinders gut secretions and protecting the underlying mucosa from toxins and other irritants [87]. According to Mehta [88], the most common types of ulcer are duodenal, peptic, and gastric ulcer. C. caesia has signifcant ulceroprotective efect against gastric ulcer, which is comparable to standard drug ranitidine [28]. A signifcant reduction of ulcer index, gastric acid volume, pepsin, free and total acidity, along with increased production gastric mucus was detected in rats treated with ethanolic extract of C. caesia (EECC-500 mg/ kg). Te lethal dose value, LD 50 , for the extract was found to be higher than 2000 mg/kg.

Antidiabetic Properties
Sedentary lifestyle, rapid urbanization, and nutrition transition lead to the raising of global diabetic and obesity cases [89][90][91]. Improper control may cause damage to the heart, blood vessels, eyes, kidneys, and nerves, which leads to disability and premature death [92]. Tese complications are correlated with postprandial hyperglycemia, which are known due to the induction of oxidative stress causing a decline in enzyme antioxidant activity and the excessive production of free radicals [93][94][95].
According to Majumder et al. [17], the rhizome of C. caesia was found to be a potential antidiabetic agent when studied in STZ-induced diabetic rats, where it signifcantly reduced fasting blood glucose (FBG), glycosylated haemoglobin (HbA1c), and oral glucose tolerance test (OGTT) level towards normal as well as improved body weight when compared to the diabetic control group. Tey also reported methanolic C. caesia extract successfully inhibiting α-amylase and α-glucosidase with IC 50 values of 442.92 ± 10.05 μg/mL (acarbose � 154.33 ± 9.08 μg/mL) and 95.40 ± 9.74 μg/mL (acarbose � 38.63 ± 8.05 μg/mL), respectively. Te extract also showed potent glucose uptake activity in yeast cells by promoting the facilitated difusion process. Te mechanism involved in efectiveness activity of methanolic C. caesia rhizome extract in the experimental rat model might be by augmenting the endogenous antioxidant mechanism [17]. Recently, Jain and Parihar [18] investigated the antidiabetic activity of successive extracts of C. caesia rhizome. Te results indicated that ethyl acetate extract showed relatively much higher inhibition activity in α-amylase inhibition assay (97.72% ± 0.28 and IC 50 value: 63.96 μg/mL) compared to curcumin and camphor as standards. Tey also discovered the chloroform : methanol (80 : 20) fraction of C. caesia ethyl acetate to contain eucalyptol, camphor, and germacrone as antioxidant property as well as caryophyllene and β-sitosterol with antidiabetic and antioxidant properties.

Analgesic Efect.
Analgesic activity works as a painkiller or pain reliever, which is mainly used in treating or controlling numerous diseases. Analgesic agents act on the peripheral and central nervous systems by several mechanisms of action without causing loss of consciousness [96]. Methanolic extract of C. caesia is suggested to be a peripherally and centrally acting analgesic in Sawant et al.'s [19] study, in which the extract showed signifcant (p < 0.001) activity in the acetic acid-induced writhing mice model as well as in the hot plate test at doses of 200 and 400 mg/kg. Mice treated with extract at 100, 200, and 400 mg/kg signifcantly (p < 0.001) decreased the number of writhing by 11.94%, 22.38%, and 31.34%, respectively, when compared to the control group. Teir observation found that the extract dose-dependently increased the pain latency time in response to the thermal stimulation procedure. Te presence of phytochemical compounds in the extract such as alkaloids, favonoids, phenols, saponins, and tannins, may contribute to the observed activity [19]. A previous report by Karmakar et al. [22] also found analgesic activity in C. caesia by acetic acid-induced writhing and tail fick tests, which demonstrated signifcant peripheral antinociceptive actions.
Other fndings revealed that treatment with curcumin was able to lessen the thermal hyperalgesia and mechanical allodynia, as measured by an extended latency to paw withdrawal (PWL) from a noxious thermal stimulus or a mechanical stimulus. A study by Cheppudira et al. [97] reported that curcumin blocked heat-induced secretion of GRO-a and IL-8, both at basal levels, as well as heat-induced matrix metalloproteinases 1 and 3 (MMP-1 and MMP-3).
Furthermore, curcumin was found to suppress p38 MAPK activity and heat-inducedNF-kB p65 activity, which indicates that curcumin may be an efective analgesic for thermal injury pain through suppression of infammation at the site of injury.

Anticonvulsant, Muscle Relaxant, and Locomotor
Depressant. Previous fndings by Arulmozhi et al. [23] found the muscle relaxant property of C. caesia hydroalcoholic extract in the bronchioles and vasculature of the respiratory tract in rodent models. Te mechanism of action was suggested to be the ability of extract to inhibit calcium release from intracellular calcium stores and also the calcium efux from extracellular space. Other fnding reported locomotor depressant, anticonvulsant, and muscle relaxant activity of C. caesia rhizome [22]. Locomotor activity in mice was signifcantly (p < 0.001) depressed in a dose-dependent fashion by a methanolic extract of C. caesia, which indicates that the extract has CNS property in mice. Te extract also was found to signifcantly protect mice from pentylenetetrazole (PTZ)-induced convulsions by delaying the onset of convulsions and allowing the animals to recover, leading to survival. Meanwhile, in a muscle relaxant study, the extract signifcantly (p < 0.001) and dose-dependently reduced the fall-of time in mice, refecting its muscle relaxant property. In the muscle relaxant assay, the methanolic C. caesia extract induced a decrease in fall-of time due to the loss of muscle grip, implying muscle relaxation. Te results show extract induced neurological defcit by its taming or calming efect in mice, thus supporting its role of CNS-depressant [22].  Evidence-Based Complementary and Alternative Medicine antidepressant activity in TST and FST. Tey also suggested that possible mechanism of action was through the elevation of monoaminergic neurotransmitters levels in the brain due to the presence of monoamine oxidase nonselective inhibitor and attenuation of oxidative stress produced during depression, by the tannic acid present in the extract [20].

Thrombolytic Properties
A blood clot causes blockage or occlusion of a blood vessel that leads to various life-threatening diseases such as atherosclerosis, glaucoma, heart attack, and stroke. Trombolytic agents assist in dissolving the blood clot and reduce the risk of the mentioned diseases [98,99]. A study by Fathima et al. [24] found that the ethanolic extract of C. caesia showed efective properties in thrombolytic activity, whereby it signifcantly exhibited cell lysis by 49.18 ± 3.41% as compared to the positive control, streptokinase (71.54 ± 3.26%), and the negative control, water (2.96 ± 0.28%). Meanwhile, Bharathi et al. [25] discovered that the hydroalcoholic extract of C. caesia has the ability to exhibit thrombolytic activity by 38.75%, which was slightly higher compared to C. amanda with 34.74%. Moreover, the silver nanoparticle of C. caesia also showed high activity in lysing the blood clot.

Toxicity Study of C. caesia
Te toxicity of substances can be observed via study of the accidental exposures to a substance, in vitro studies using cells/cell lines, and in vivo exposure on animal models [100]. Previous toxicity studies of C. caesia were mainly conducted in vitro and in vivo. As mentioned above, in-vitro toxicity studies of the C. caesia extract have been done against EAC [101], human laryngeal cancer (Hep 2), human liver adenocarcinoma (HepG2), human colon adenocarcinoma (HT 29), monkey kidney (VERO) [102], and human acute monocytic leukemia (THP-1) cell lines [32], which all demonstrated the toxicity efects of the plant. Meanwhile, acute toxicity studies in experimental animals (mice and rats) have been done up to several high doses, including 1000 [37], 2000 [17,19,28], and 3000 [36] mg/kg body weight per oral administration. All reported survival of the animals after administration of the plant extract, thus revealed that the LD 50 is higher than that amount of dose tested.
Besides, the toxicity of a substance can also be monitored through biochemical parameters, such as the liver and kidney marker enzymes that are commonly used to quantitatively evaluate the degree of damage to the organs [76]. A study by Hadem et al. [37] reported that diethylnitrosamine (DEN)-treated mice showed a signifcant reduction of serum transferases (alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP)) towards their control as observed after 16 and 28 weeks. Tis result tallied with a study by Devi and Mazumder [38] that reported signifcant reductions in SGOT and SGPT levels in cyclophosphamide (CP)-treated mice compared to the positive group and another study by Majumder et al. [17] that reported that the ALP level in the C. caesiaextract-treated group was signifcantly (p < 0.05) lowered compared to the STZ control group.
Another form of toxicity study, known as the Allium cepa assay, is chemical screening and in situ monitoring for genotoxicity of environmental contaminants, such as pesticides, which help detect if these compounds can induce chromosomal aberrations in the root meristems of A. cepa [103,104]. Borah et al. [42] discovered that C. caesia leaf essential oil possesses a negligible amount of genotoxic action towards root growth test, mitotic index, and chromosomal aberrations in the Allium cepa assay, as compared to the positive control ethyl methanesulfonate (EMS). Tey also claimed that the C. caesia leaf essential oil is potentially safe to be used in pharmaceutical and industrial applications.

Effort on Plant Conservation
Tis plant is currently considered as endangered species due to the extensive traditional human usage, low multiplication rate in the soil, root susceptibility to disease caused by parasitic fungi, Pythium species [10], as well as industrialization and urbanisation, which destroyed their natural habitat [105]. However, a new propagation method is needed for this plant due to the minus points of the conventional method, including (i) that 10-20% of the yield is required for raising the next crop, (ii) the risk of soil-borne diseases from one crop to the next and from one location to another, and (iii) the necessity of proper preservation of the seed rhizomes during the gap period between harvesting and raising the next crop, as they are prone to rhizome rot caused by bacteria, fungi, and insect attacks [106]. Currently, in vitro cell and tissue culture methodologies are widely used as a means for plant conservation to ensure the survival of endangered species. Besides, this method requires only small explants for micropropagation and high multiplication rates for large-scale revegetation and is able to produce diseasefree plants [107]. Tus, in order to conserve the species from extinction, initiatives have been taken by researchers through plant cells and tissue culture approaches [9].

Conclusion
Most people are now shifting from using synthetic to natural-based products due to the safety issue. Medicinal plants and herbs are studied extensively, leading to numerous promising discoveries. C. caesia is one of the herbal plants currently gaining popularity among researchers due to its potential health benefts. Overall, it can be concluded that C. caesia has the potential to be explored as a natural complementary and alternative health therapy with potential for the pharmaceutical and nutraceutical industries. Research reports on C. caesia suggest its medicinal and pharmaceutical potentials might be due to the variety of metabolites in the plant that give the efects observed, which can be determined by an advanced metabolomics approach. Terefore, authors are currently investigating the plant metabolites through the NMR analysis and bioactivity variations associated with diferent solvent ratios that hypothesized absolute ethanol extract to be most excellent 12 Evidence-Based Complementary and Alternative Medicine extract with abundance of metabolites, which are responsible for the bioactivities [108,109].
Te uses of C. caesia due to its potential health benefts to humans are gaining interest by researchers. Several scientifc studies have found the antioxidant, antibacterial, antifungal, antiproliferative, anticancer, anti-infammatory, analgesic, and anticonvulsant properties as well as the muscle relaxant, locomotor depressant, antidepressant, and thrombolytic activities of C. caesia. Further studies are required to identify, isolate, and elucidate the structures of novel bioactive constituents present in C. caesia that contribute to its health benefts. Besides, more evidence, especially through in vivo and clinical trials, is necessary to determine the mechanisms involved in the bioactivities mentioned previously. Even though there are available preliminary data on the nutritional values of C. caesia rhizomes, information is still lacking, especially on other parts of the plant, such as the leaves, stem, and fower. Tus, studies on the leaves, stem, and fower of C. caesia could also be done to discover potential bioactive compounds that can be exploited for health advantages.

Data Availability
Te data used to support the fndings of this study are included within the article. Any other data can be available upon request from the corresponding author.

Conflicts of Interest
Te authors declare that there are no conficts of interest regarding the publication of this article.