Phytochemistry and Biological Properties of Salvia verbenaca L.: A Comprehensive Review

The family Lamiaceae contains several plants used in traditional medicine to fight against different diseases. Salvia verbenaca L. (S. verbenaca) is one of the Lamiaceae species distributed around the Mediterranean regions. This plant exhibits different bioactive properties, including antibacterial, anticancer, antioxidant, antileishmanial, antidiabetic, immunomodulatory, and wound healing. This review was conducted to revise previous studies on S. verbenaca addressing its botanical description, geographical distribution, and phytochemical, pharmacological, and toxicological properties. Moreover, the main pharmacological actions of S. verbenaca major compounds were well investigated. Literature reports have revealed that S. verbenaca possesses a pivotal role in medicinal applications. The findings of this work noted that S. verbenaca was found to be rich in chemical compound classes such as terpenoids, phenolics, fatty acids, sterols, and flavonoids. Numerous studies have found that S. verbenaca essential oils and extracts have a wide range of biological effects. These results support the potential pharmacological properties of S. verbenaca and its traditional uses. This analysis can constitute a scientific basis for further refined studies on its pure secondary metabolites. Therefore, the outcome of the present work may support the perspective of identifying new therapeutical applications with detailed pharmacological mechanisms of S. verbenaca to prevent the development of some diseases such as neurodegenerative disorders. However, toxicological investigations into S. verbenaca are needed to assess any potential toxicity before it can be further used in clinical studies.


Introduction
Since the beginning of time, medicinal plants have been and continue to be the primary source of medicine [1]. Salvia verbenaca L. (S. verbenaca) is a medicinal herb belonging to the family Lamiaceae, which is the most representative genus of Salvia [2,3]. This plant is endemic to the Mediterranean region, including Morocco, Canaries Islands, Algeria, Tunisia, Libya, Egypt, and Cyprus, and has also spread to Europe and Asia [4]. In traditional medicines, S. verbenaca has been used to fight against numerous diseases; several ancient and current investigations revealed that S. verbenaca presents a chemical diversity in terms of chemical composition according to the chemical characteristics of the extracts from various parts. Indeed, S. verbenaca contains numerous secondary metabolites that belong to a wide variety of phytochemical classes [5]. S. verbenaca terpenoids have been revealed to have a large diversity due to several factors, including genetic, ecological, environmental, edaphic, and diverse plant parts [6]. An antibacterial potential against a wide range of gram-positive and gram-negative bacteria has been documented [7][8][9][10][11]. Consequently, the antibacterial efficacy of extracts and essential oils (EO) from S. verbenaca was remarkable against gram-positive bacteria compared to the gram-negative bacteria. Furthermore, S. verbenaca was found to have an antioxidant effect against free radical damage [12] and significantly reduce the level of intracellular reactive oxygen species (ROS) [13,14]. According to previous studies, the anticancer properties of S. verbenaca extracts and essential oils have also been reported [15][16][17][18][19]. The antiparasitic properties of S. verbenaca, in particular, antileishmanial effects, have been investigated elsewhere [20].
Besides, S. verbenaca was reported to have an inhibitory effect of xanthine oxidase [21] and a healing effect on burns [22]. Furthermore, S. verbenaca revealed immunomodulatory effects [23]. Furthermore, the toxicological tests found that the ethanolic extract of S. verbenaca did not cause any toxic symptoms or death in rats [24].
The objective of the current article was to provide a general review of S. verbenaca such as botanical description, geographical distribution, phytochemistry, and pharmacological properties. Hopefully, this analysis could be a scientific basis for further refined studies on pure compounds from S. verbenaca that may lead to the identification of new therapeutical applications.

Research Methodology
All data about S. verbenaca (botanical description, taxonomy, destruction, phytochemical, and pharmacological properties) were collected using several databases like Web of Science, Google Scholar, Scopus, ScienceDirect, Springer-Link, Wiley Online, PubMed, and SciFinder and were reviewed in order to compile literature on S. verbenaca. The structures of the chemical profiles were identified in S. verbenaca, and the ChemDraw Pro 8.0 software was used to create the illustrations.
2.1. Botanical Description. S. verbenaca is a perennial herb that reaches between 10 and 50 cm (in height), hairy at the top, odorous, more or less glandular at the top. It grows in the dry lawns, the slopes, and at the edges of the paths. The slightly branched stems carry bunches of dark blue flowers in spring. Leaves are oblong, 2-3 cm broad, crenelated or incised-lobed, with the upper stalkless ( Figure 1). The flowers are quite small, pale blue or whitish, in whorls usually close together, forming a fairly short cluster; the fruiting calyx with almost closed lips, bristling with spread hairs; the corolla is 10-15 mm, twice as long as the calyx, with wide lips, very uneven, the upper one compressed and curved in a false shape, and the style with little or prominent point [25].
2.2. Geographic Distribution. S. verbenaca has a very wide geographical distribution around the Mediterranean region, including Morocco, Algeria, Tunisia, Canaries, Egypt, Libya, Turkey, Cyprus, Transcaucasia, and Western and Southern Europe. It is also grown in South West Africa, North America, and Australia [5].

Ethnomedicinal Uses.
The ethnobotanical investigations into S. verbenaca revealed its wide applications in folkloric medicine to treat numerous disorders as listed in Table 1. In Morocco, its application in folk medicinal systems includes the treatment of some digestive disorders such as abdominal colics [26][27][28]. The most commonly used part of the plant is the aerial part, which is prepared by infusion before being used to treat respiratory problems and genitourinary and skin diseases [27]. Dried leaves are also used for the treatment of wounds, burns, and abscesses [29]. Aerial parts are utilized in decoction or infusion to treat diabetes [30].

Phytochemistry.
Like all medicinal plants belonging to the family Lamiaceae, S. verbenaca contains numerous secondary metabolites with different classes, such as flavonoids, terpenoids, alkaloids, and phenolic acids. Currently, several analytical investigations using different technical tools (GC, GC-SM, GC-MS, GC-FID, HPLC, 1D and 2D NMR, IR, UV, 1H NMR, and 13C NMR) have been applied to identify and isolate bioactive compounds from medicinal plants. Indeed, investigations into the chemical constituents of S. verbenaca revealed the presence of terpenoids, phenolics, fatty acids, flavonoids, and sterols ( Table 2). As listed in Table 2, the chemical content of S. verbenaca was investigated in different areas with various medicinal applications by using different analytical tools. The results are different according to numerous factors, such as the study area, plant part used, and adopted methodology.
Al-Jaber et al. [25] compared the different parts of S. verbenaca volatile compounds collected from two locations in Jordan. Monoterpene hydrocarbons dominated the emission profile of stem, sepal, and leaf samples from the Mediterranean zone (68.0%, 33.7%, and 42.2%, respectively). Oxygen-ated monoterpenes controlled the production and emission of flowering components, including preflowering buds, fully grown flowers, and petals. Also, Taârit et al. [33] showed that the major compounds in EOs in Salvia aerial parts from the three Algerian regions were the monoterpene hydrocarbons and oxygenated sesquiterpenes. Additionally, the influence of collecting locations and phenophases on the production and chemical composition of S. verbenaca L. essential oils was examined by Farhat et al. [6]. In this study, it was reported that at the floral stage, monoterpene hydrocarbons (31.9%) prevail, whereas oxygenated sesquiterpenes (27.5%) predominate at the early fruiting stage. Sesquiterpene hydrocarbons were the most abundant chemical class at late fruiting (28.2%). Furthermore, Al-Jaber [32] reported that S. verbenaca EO was primarily composed of oxygenated monoterpenes (61.32%), with the monoterpene alcohol linalool serving as the sole monoterpene alcohol, whereas the essential oil obtained from the air-dried plant was primarily composed of sesquiterpene hydrocarbons (62.66%), with germacrene D serving as the major component (25.92%).
The investigation of the methanol extract from aerial parts of Tunisian S. verbenaca demonstrated that the extract had a high antibacterial potential (MIC = 500 μg/mL) against six bacteria isolated from the mouths of patients [42]. However, a South African extract of S. verbenaca that was made with methanol and chloroform had strong antibacterial properties against Klebsiella pneumoniae, Bacillus cereus, Escherichia coli, and Staphylococcus aureus [11]. Moreover, Belkhiri et al. [21] compared the antibacterial potential of four fractions from the methanol extract of Algerian S. verbenaca: chloroform extract, crude extract, aqueous extract, and ethyl acetate extract. They have found that the antibacterial efficacy increases with the concentration of the extract. Al-Zereini [7] also found that the ethyl acetate extract prepared from the leaves of S. verbenaca from Jordan had dose-dependent antibacterial properties against Bacillus brevis (ATCC 9999) and Bacillus subtilis (ATCC 6633). On the other hand, the extract had no effect on Klebsiella pneumoniae (ATCC 13883), Staphylococcus aureus (ATCC 43300), and Escherichia coli (ATCC 25922). Canzoneri et al. [8] found that the EO of S. verbenaca aerial parts has potential antibacterial effects, and this activity is much higher against gram-positive bacteria than gram-negatives.

Antioxidant
Activity. The antioxidant potential of S. verbenaca extracts was investigated by several researchers [12,21,23,38,[42][43][44], and Table 4 summarizes the majority of the investigations that were carried out on different parts of S. verbenaca, collected from different regions.
Kostić et al. [41] evaluated the antioxidant potential of different S. verbenaca extracts using the beta-carotene/linoleic acid system and DPPH assay. They found that the methanol extract had the highest activity in the DPPH method, while the ethanolic extract obtained by ultrasound extraction was the most active metabolite of beta-carotene/linoleic acid. The antioxidant activity of hydromethanolic extract prepared from stems and leaves of Moroccan species was carried out by Khlifi et al. [44]. The results showed that the extract had a significant antioxidant effect at 100 μg/mL,  14 BioMed Research International with a strong inhibition of oxygen consumption compared to previous studies [38]. The antioxidant potential of Tunisian S. verbenaca extracts was also studied [42], and the results showed that methanolic extract from aerial parts had lower activity (IC 50 = 86:9 μg/mL) compared to the positive control, which was the trolox (IC 50 = 23:12 μg/mL) using the DPPH assay. In addition, it was reported that the antioxidant activity over 20 minutes using the ABTS assay increased with time, but was still four times lower than the activity of trolox.     19 BioMed Research International Additionally, Farhat et al. [6] studied the efficacy of the collection sites on the antioxidant capacity of methanolic extract prepared from postdistilled aerial parts of Tunisian species. They found that the site had a significant effect on the antioxidant potential by the DPPH, ABTS, and FRAP methods. Likewise, activity was shown to be substantially linked with total phenolic content.

BioMed Research International
The antioxidant activity of some extracts of S. verbenaca collected from Algeria was mostly studied using the DPPH assay. It was found that the crude extract prepared from aerial parts had good antioxidant activity that increased with increasing the extract concentration [14]. The scavenging activity was 95% at a concentration of 0.1 mg/mL. Also, the methanol extract of S. verbenaca aerial parts revealed a high reducing power in the FRAP test [43] using the DPPH assay. Additionally, it was cited that the methanol extract had a beneficial effect against free-radical damage and exhibited a 5-fold more inhibitory effect than the standard antioxidant trolox (IC 50 = 72:63 μM) [12]. They also observed that the radical scavenging activity had no significant correlation with the phenolic content and a low correlation with the flavonoid content. Belkhiri et al. [21] investigated the antioxidant potential of some fractions of the methanol extracts using the DPPH method, metal chelating activity, and reducing power assay, and all extracts showed potent antioxidant activity [13]. The cupric ion reducing capacity (CUPRAC) and Fe 3+ reducing capacity (phenanthroline assay) of the extracts were investigated, and the findings exhibited that both extracts had high antioxidant capacity, with methanolic extract exhibiting the highest activity [14].
2.5.3. Anticancer Activity. The different organic essential oils and extracts of S. verbenaca have been studied for anticancer properties. Numerous laboratory investigations using cell culture have shown that S. verbenaca extracts and essential oils have antiproliferative properties (Table 5) against a variety of cancer cell lines [15-19, 23, 45].  20 BioMed Research International The ethyl acetate extract of S. verbenaca leaves produced after maceration was examined using the MDA cell lines MB-231 (human breast adenocarcinoma, ATCC HTB-26). The findings indicated that all extracts produced cytotoxicity in MDA MB-231 breast cancer cells [7]. However, it was proved that S. verbenaca leaf extracts possessed cytotoxic effect against HEp-2 (human larynx cancer cells) and Vero (monkey kidney cells) [18]. In another investigation, methanolic extracts of S. verbenaca's aerial component prepared by maceration were evaluated in vitro against four human cancer cell lines, including HCA, HepG2, MCF-7, and HPC. The findings indicate that LC 50 levels higher than 75 μg/ mL were deemed inactive [15]. Additionally, MTT assays were used to determine the cytotoxic activity of several extracts (methanol, hexane, ethyl acetate, n-butanol, and chloroform extracts) obtained from the aerial portion of S. verbenaca [16]. Methanol and chloroform extracts of S. verbenaca aerial parts were evaluated against colon adenocarcinoma (HT-29), human cancer cell lines (breast adenocarcinoma (MCF-7), human kidney epithelial cell line and glioblastoma (SF-268)) [17]. S. verbenaca exhibited more favorable action against MCF-7, with an IC 50 value of 31.50 13.70 μg/mL, but was inactive versus SF-268 and/ or HT-29 cell lines [17].
A cell viability study was performed to avoid any cytotoxic concentration of S. verbenaca root extract on THP-1 cells. The MTT assay revealed that the most cytotoxic concentration of the extract was 1000 μg/mL, which caused 70% of cell death and 30% of cell viability [23]. The essential oils of S. verbena were investigated for their ability to suppress the proliferation of human tumor cells using the human M14 melanoma cell line and shown significant efficacy [19]. The antiproliferative effect of S. verbenaca essential oil may be attributed to active sesquiterpenes in combination with other natural chemicals found in the essential oil components. Indeed, carvacrol and thymol exhibited outstanding anticancer properties through a variety of mechanisms [19].
2.5.4. Antiparasitic Activity. Et-Touys et al. [20] investigated the antileishmanial effects of organic extracts (methanol, nhexane, and dichloromethane extract) from S. verbenaca, and it was reported that the in vitro antileishmanial effect which was evaluated on the culture of three Leishmania species such as Leishmania infantum, Leishmania tropica, and Leishmania major was good (Table 6).
Belkhiri et al. [21] additionally observed that S. verbenaca has antihemolytic properties. In vitro antihemolytic  [14] 22 BioMed Research International activity of S. verbenaca extract was determined by inducing oxidative erythrocyte hemolysis. The results indicated that ethyl acetate extract was the most effective in inhibiting hemolysis, followed by crude extract, chloroform extract, and aqueous extract. Additionally, ethyl acetate extract inhibited hemolysis more effectively than vitamin C.
2.5.5. Insecticidal Activity. In most cases, the application of synthetic pesticides is the primary approach for controlling insect pests, which produces excellent effects in a short period of time. Meanwhile, their irrational usage has resulted in global issues such as pollution, nontarget toxicity, biodiversity loss, and the development of pest resistance [46][47][48]. This need arose from a desire to provide alternatives to synthetic insecticides, which can have negative environmental consequences [49][50][51][52]. The insecticidal capabilities of S. verbenaca extracts and essential oils have been documented to have potential impact against several pests in previous studies [53]. Insecticidal action has been shown in several experiments using some Salvia species [54]. Essential oils from Salvia species revealed 100% repellency activity against adults of Aedes albopictus [55]. The oil of S. verbenaca drastically shortened the lifespan of cowpea weevil and prevented females from laying eggs [56]. Several crude extracts and essential oils from Salvia species were tested for pesticide activity against the test pest larvae [57][58][59]. Insectistatic and insecticidal properties of chloroform extracts from the aerial portions of four Salvia species were examined [60]. S. verbenaca extracts are very effective against Culex quinquefasciatus mosquitos [61]. Caryophyllene oxide was the major component in the essential oil of S. verbenaca with 7.28 [62]. The insecticidal activity and fumigant toxicity of caryophyllene oxide were tested against two insect pests, and it was shown to be effective [63].
2.6. Other Biological Effects. Different extracts from S. verbenaca have also exhibited other biological activities such as antihemolytic, immunomodulatory, and enzyme inhibitory effects (Table 7).
2.6.1. Xanthine Oxidase Inhibitory Effect. Xanthine oxidase, abbreviated as XO, is an oxidoreductase that catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid. Xanthine oxidase is generally present in the liver and in an inactive form in the blood in humans. A blood test for XO may identify liver impairment because xanthine oxidase is released into the blood in situations of severe liver injury [21].
2.6.2. Burn Recovery Activities. Guaouguaou et al. [24] evaluated the impact of three S. verbenaca extracts on the healing of burns in rats using hexane, ethyl acetate, and nbutanol. The results indicated that various Salvia verbenaca plant extracts were more effective than silver sulfadiazine (SSD) and that it is the most widely used topical treatment for injury, with healed areas of 29.17% (base), 44.34% (hexane), 47.55% (ethyl acetate), 49.16% (n-butanol), and 41.09% SSD.

24
BioMed Research International 2.6.3. In Vitro Antidiabetic Activity. Several earlier studies have shown S. verbenaca's antidiabetic activity in vitro [13]. Additional studies are shown in Section 2.8 and Figure 8.

Immunomodulatory Effects.
Previous studies investigated the immunomodulatory effects of S. verbenaca aerial parts [14]. The carbon clearance rate test was used to determine the immunostimulant potential of this plant on phagocytic activity. The phagocytic index was much higher in rats who were given S. verbenaca at a dose of 200 mg/kg than in rats who were not given the herb.

Toxicological
Investigations of S. verbenaca. The toxicological investigations of S. verbenaca have not been well studied. However, some studies carried out recently have confirmed the safety of these plant extracts (Table 8). Indeed, a report by Guaouguaou et al. [64] focused on the acute and subchronic effects of S. verbenaca toxicity in mice and rats through oral and topical administration. The findings of the acute toxicity of the fractions derived from S. verbenaca (n-butanol, hexane, and ethyl acetate) demonstrated that the LD 50 of this plant after oral administration at 2000 mg kg -1 is not deadly [64]. In order to complete the toxicity profile of this plant, more research should be done to find out how toxic it is over a long period of time.

Pharmacological Properties of S. verbenaca Main Volatile
Compounds. Several studies examined the major volatile chemicals found in S. verbenaca, including carvacrol, thymol, and linalool. Studies showed that carvacrol has hypoglycemic properties through intrinsic mechanisms such as blood glucose and insulin level lowering [65]. Additionally, carvacrol resulted in a drop in glucose levels. Additionally, these substances were shown to enhance the activity of glucokinase and glucose-6-phosphate dehydrogenase in the liver [66]. Carvacrol inhibits the enzymes α-amylase and alpha-glucosidase in vitro [67] and beta-galactosidase in vitro [68]. Thymol was also able to normalize blood sugar, plasma insulin, HbA 1c , and the insulin resistance index in patients with hyperglycemia [69]. The levels of expression of genes involved in the production of insulin have been studied and reported in STZ-induced diabetic mice [70,71], and a rise in Mafa and Pdx1 gene expression has been reported. Limonene is another major constituent of S. There are no harmful symptoms or changes in the amount of water or food consumed There is no lethality There is no change in the parameters of fasting blood circulation There were no morphological alterations in the main vital organs investigated

BioMed Research International
verbenaca that has been shown to improve glucose homeostasis. Indeed, this substance boosts hepatic glycogen and plasma glucose levels [72] (Figure 8).
The major phytochemical compounds of S. verbenaca exhibited remarkable antibacterial effects [75][76][77]. Rhayour et al. [70] investigated the impact of thymol on grampositive and gram-negative microorganisms, including Bacillus subtilis and Escherichia coli [75][76][77][78]. Antibacterial activity is demonstrated by modifying cell shape, damaging cell walls and membranes, and limiting the development of some types of bacteria, including P. aeruginosa [79]. In addition, limonene was found to be antibacterial because it targeted microorganisms' cytoplasmic membranes, weakened membrane integrity, blocked respiratory enzymes, and lost the proton motive force (Figure 9).
The anticancer properties of the major components in S. verbenaca (carvacrol, limonene, and thymol) have also been reported recently [80][81][82]. Thymol has been shown to have anticancer properties via a variety of mechanisms, including inducing severe DNA damage, including the production of reactive oxygen species (ROS) and subsequent increase in oxidative stress and/or mitochondrial dysfunction, or via the nuclear factor of activated T cell (NFAT-2) route [81]. Additionally, carvacrol increased apoptosis in cells, perhaps via activating mitochondrial apoptotic and signaling pathways [83].

Conclusions and Perspectives
S. verbenaca, a medicinal plant used in traditional medicine to cure a variety of ailments, was found to be abundant in bioactive chemicals such as flavonoids, terpenoids, and phenolic acids. Numerous pharmacological studies have demonstrated that S. verbenaca extracts and essential oils have extraordinarily beneficial effects on a variety of diseases, including those caused by microbes and those caused by dysregulation of homeostasis. Indeed, this plant demonstrated antibacterial, antidiabetic, anticancer, and immunomodulatory properties via a variety of mechanisms. However, further research should be conducted to find other pharmacodynamic targets. Additionally, pharmacokinetic studies should be conducted to ascertain the absorption, metabolism, and elimination of S. verbenaca bioactive components. Additionally, toxicological studies should be conducted to validate the safety of S. verbenaca extracts at various doses and delivery methods.

Data Availability
All the data are cited in the main text of this document.

Conflicts of Interest
No potential competing interest was reported by the authors.