Evidence-Based Complementary and Alternative Medicine
Volume 2015 (2015), Article ID 506413, 9 pages
http://dx.doi.org/10.1155/2015/506413

Research Article

In Vitro Pharmacological Activities and GC-MS Analysis of Different Solvent Extracts of Lantana camara Leaves Collected from Tropical Region of Malaysia

Mallappa Kumara Swamy,¹ Uma Rani Sinniah,¹ and Mohd. Sayeed Akhtar²

¹Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
²Institute of Tropical Agriculture, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia

Received 18 September 2015; Revised 19 November 2015; Accepted 22 November 2015

Academic Editor: Rahmatullah Qureshi

Copyright © 2015 Mallappa Kumara Swamy et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

We investigated the effect of different solvents (ethyl acetate, methanol, acetone, and chloroform) on the extraction of phytoconstituents from Lantana camara leaves and their antioxidant and antibacterial activities. Further, GC-MS analysis was carried out to identify the bioactive chemical constituents occurring in the active extract. The results revealed the presence of various phytocompounds in the extracts. The methanol solvent recovered higher extractable compounds (14.4% of yield) and contained the highest phenolic (92.8 mg GAE/g) and flavonoid (26.5 mg RE/g) content. DPPH radical scavenging assay showed the IC₅₀ value of 165, 200, 245, and 440 μg/mL for methanol, ethyl acetate, acetone, and chloroform extracts, respectively. The hydroxyl scavenging activity test showed the IC₅₀ value of 110, 240, 300, and 510 μg/mL for methanol, ethyl acetate, acetone, and chloroform extracts, respectively. Gram negative bacterial pathogens (E. coli and K. pneumoniae) were more susceptible to all extracts compared to Gram positive bacteria (M. luteus, B. subtilis, and S. aureus). Methanol extract had the highest inhibition activity against all the tested microbes. Moreover, methanolic extract of L. camara contained 32 bioactive components as revealed by GC-MS study. The identified major compounds included hexadecanoic acid (5.197%), phytol (4.528%), caryophyllene oxide (4.605%), and 9,12,15-octadecatrienoic acid, methyl ester, (Z,Z,Z)- (3.751%).

1. Introduction

Nature has existed as a source of almost all drugs for many years and natural products were the only source of medicine for mankind ever since the ancient period. Herb based products play an important role in primary human health care as the majority (80%) of the global population rely on traditional medical practices [1, 2]. Most of the modern drugs are derived either from plant sources or from their derivatives for various medicaments and are extensively used in the pharma industry [2]. In addition to the prevailing health problems, emerging infectious diseases and disorders have seriously caused the world population to suffer with a high mortality rate. It is reported that about 50% of all fatality occurring in tropic countries is mainly due to the current infectious diseases [3]. Also, increase of antimicrobial resistance among the pathogens is a rising problem which is challenging the scientific advancement of the medical world [4]. This situation has prompted researchers to develop efficient new antimicrobial agents. Therefore, exploration of natural products as leads to discover new drug molecules is continuously made to understand their therapeutic potential with special reference to biological activities, efficiency, and safety aspects. Exploration of medicinal plants for curative purposes is mainly based on the available traditional information from the experts and local population [5, 6].

Lantana camara L. is a medicinal aromatic plant that belongs to the family Verbenaceae and occurs in most parts of the world as an evergreen notorious weed species. It is also considered as an ornamental garden plant. It is widely used in different traditional medical practices for treating various health problems. Different parts of the plant are used in treating various human ailments such as measles, chicken pox, tetanus, malaria, cancers, asthma, ulcers, fevers, eczema, skin rashes, cardiac disorders, and rheumatism [7, 8]. Also leaf extracts and essential oil of L. camara leaves possess larvicidal activities, antioxidant, anti-inflammatory, analgesic, antidiabetic, hypolipidemic, anthelmintic, wound healing, and antipyretic properties [9, 10]. The therapeutic potential of the plant is due to the occurrence of many bioactive phytocompounds such as terpenoids, alkaloids, flavonoids, phenolics, glycosides, and steroids as major phytoconstituents [11]. Some of the important bioactive compounds include quercetin, isorhamnetin, oleanolic acid, lantadene A, β-sitosterol pomonic acid, camaric acid, verbacosides, lantanoside, linaroside, octadecanoic acid, palmitic acid, and docosanoic acid. The essential oil from the leaves is rich in monoterpenes and sesquiterpenes [11–13]. Various factors including genetic, geographical location, plant parts, and environmental factors have been shown to influence the accumulation of phytochemical contents in different parts of L. camara and its essential oil composition [14–16]. Also, occurrence of varietal differences in phytoconstituents of L. camara has been documented by Sharma et al. [17]. More recently, in vitro study indicated the existence of chemical differences in methanol leaf extract of four varieties of L. camara collected from India and their antioxidant property was found to differ [8]. Certainly, more research efforts should be carried out to explore the potential benefits of L. camara for treating various health problems. Therefore, the present investigation was aimed at determining the phytochemical constituents and antioxidant and antimicrobial activities of different solvent extracts of L. camara leaves collected from the tropical region of Malaysia. Moreover, the bioactive components of the extracts were also identified using GC-MS analysis.

2. Materials and Methods

2.1. Plant Collection

L. camara plant material was collected from the forest area near Universiti Putra Malaysia, Serdang, Selangor, Malaysia, during the month of May 2015. Plant material was authenticated by N. A. P. Abdullah, Department of Crop Science, Universiti Putra Malaysia, Malaysia, and the voucher specimen (LC-102015) was deposited at the department. The leaves were detached from the collected materials, washed with water and dried under shade for 1 week, and finely powdered using electric blender. The powdered material was kept at room temperature for future use.

2.2. Preparation of Extracts

Five grams of powdered leaves was kept in a beaker to which 100 mL of various organic solvents (ethyl acetate, methanol, acetone, and chloroform) was added and thoroughly shaken. Later the mixture was placed at room temperature for 48 hrs and stirred 2-3 times a day. After filtering the mixture, the filtrate was evaporated to dryness using Rotavapor. The final extracts were weighed to determine the yield (%) and the dried extracts were stored at 4°C in a refrigerator for further studies.

2.3. Phytochemical Screening

The presence of various phytochemical constituents such as alkaloids, saponins, flavonoids, phenolics, anthraquinones, tannins, cardiac glycosides, steroids, and terpenoids was screened qualitatively by using standard procedures [18–20].

2.4. Determination of Total Phenolic and Flavonoid Contents

Total phenolic contents present in different solvent extracts were determined by using FC (Folin-Ciocalteu) colorimetric method as detailed by Salar and Seasotiya [21]. About 0.1 g of dried extract was suspended in 1 mL of the respective solvents and 0.1 mL of this solution was mixed thoroughly with 1 mL of sodium carbonate (20%) solution and 0.5 mL of 50% FC reagent. Thereafter, the solution was allowed to remain at room temperature for about 20 min to observe the color change. The absorbance was taken against the blank (water) at 730 nm. Using different concentrations of gallic acid, a standard calibration curve was generated. Total phenolic content was represented as mg of gallic acid equivalents (GAE) per gram of dried extract.

Total flavonoids content present in different solvent extracts was verified by the modified procedure of Zhishen et al. [22] using colorimeter. Briefly, 2 mL of distilled water was mixed well with 0.5 mL of solvent extract. Thereafter, 150 μL of NaNO₂ solution (5%) was added and kept for 5 min at room temperature. It was followed by adding 600 μL of AlCl₃ (10%) and 2 mL of NaOH (4%). After mixing thoroughly, the solution was made up to 5 mL with distilled water and set aside for 15 min at room temperature. By using water as blank, absorbance was measured at 510 nm. A standard calibration curve was generated using different concentrations of rutin. Total flavonoid content was articulated as mg of rutin equivalent (RE) per gram of dried extract.

2.5. Antioxidant Activity

2.5.1. Free Radical Scavenging Activity

The antioxidant activity of each extract was assessed using DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging assay as explained by Mohanty et al. [23] with little modifications. In short, 0.3 mL of different extract at varied concentrations (100–1000 μg/mL) was mixed with 2 mL of 0.1 mM DPPH solution and incubated for 30 min under dark conditions at room temperature. Afterwards, using UV-visible spectrophotometer, the absorbance was taken at 517 nm against methanol (blank) while ascorbic acid served as a standard sample. The reaction mixture showing lower absorbance is an indication of higher activity of radical scavenging. The inhibition percentage of free radical scavenging was calculated based on the following formula:

For each extract, IC₅₀ values (the minimum quantity of extract necessary for scavenging free radicals up to 50%) were calculated from the standard plot.

2.5.2. Hydrogen Peroxide (H₂O₂) Scavenging Activity

The potential capacity of different solvent extracts to scavenge H₂O₂ was carried out by the method outlined by Mohanty et al. [23]. In brief, various quantities of plant extract (100–1000 μg/mL) were prepared as detailed in previous experiment. By using phosphate buffer (pH 7.4), H₂O₂ solution (4 mM/L) was prepared. Varied amounts of plant extracts were mixed with 0.6 mL of H₂O₂ solution and kept for 30 min incubation at room temperature. The activity of H₂O₂ was analyzed by taking absorbance at 230 nm using phosphate buffer without H₂O₂ as blank solution. H₂O₂ scavenging activity (%) was calculated by using the following equation:

For each extract, IC₅₀ value (the minimum quantity of extract necessary for scavenging free radicals up to 50%) was calculated from the standard plot.

2.5.3. Determination of Antibacterial Activity

The antibacterial activities for the extracts were evaluated by using disc diffusion method. The experiment included both Gram positive (Micrococcus luteus, Bacillus subtilis, and Staphylococcus aureus) and Gram negative (Escherichia coli and Klebsiella pneumoniae) pathogenic strains of bacteria. One mg of each extract was dissolved in 1 mL of DMSO (dimethyl sulfoxide) and about 2.5, 5.0, and 10 μL of this solution were impregnated on sterilized filter paper discs (6 mm size). The discs were kept on the nutrient agar medium preinoculated uniformly with the known bacterial culture. The discs soaked with chloramphenicol (50 μL of 50 μg/mL) served as positive control while discs soaked with 50 μL DMSO served as negative control. All culture plates were kept in an incubator at 37°C for 24 h and the bacterial inhibition zone was recorded and expressed in mm. For each bacterial strain, the test was repeated 3 times.

2.6. GC-MS Analysis

GC-MS analysis of the active methanol extract of L. camara was carried out by using the GC-MS instrument (Model GCMS-QP2010 Ultra, Shimadzu Co., Japan) equipped with a capillary column DB-1 (0.25 μm film × 0.25 mm i.d. × 30 m length). The instrument was operated in electron impact mode at ionization voltage (70 eV), injector temperature (230°C), and detector temperature (280°C). The carrier gas used was helium (99.9% purity) at a flow rate of 1 mL/min and about 1 μL of the sample was injected. The oven temperature was initially programmed at 80°C (isothermal for 5 min.) and then increased to 200°C at 5°C/min and finally to 280°C at 5°C/min (isothermal for 16 min). The identification of compounds from the spectral data was based on the available mass spectral records (NIST and WILEY libraries).

2.7. Statistical Analysis

All the data measured in each experiment included 3 replications () and the results were represented as mean ± SD. The one-way analysis of variance (ANOVA) was performed to compare the data and Tukey’s test was used to find out the statistically significant differences at using statistical software, GraphPad Prism version 5.0.

3. Results and Discussion

The results of preliminary investigation on the phytochemicals present in different solvent extracts of L. camara are presented in Table 1. Different phytocompounds such as alkaloids, saponins, flavonoids, phenolics, anthraquinones, tannins, cardiac glycosides, steroids, and terpenoids were detected in the crude extracts. Flavonoids, phenolics, and cardiac glycosides were noticed in all solvent extracts used. Methanol extracts with 7 phytoconstituents were the best among the organic solvents evaluated in our study. Acetone extract showed the presence of 6 phytoconstituents while ethyl acetate and chloroform extracts contained 5 phytocompounds. All these identified phytochemicals are known to have a wide range of biological activities including antibacterial, antifungal, antiviral, antioxidant, and cytotoxic properties [19]. Understanding the occurrence of phytochemicals in medicinal plants is advantageous and presently, the discovery of new drug compounds or lead molecules from plants is mainly based on the systematic examination of different plant extracts or plant based products. Also, this preliminary knowledge can decipher a new source for economically valued chemical compounds [1, 23].

Table 1: Qualitative screening of phytochemicals present in different solvent extracts of L. camara leaves.

Phytochemicals
Ethyl acetate
Methanol
Chloroform
Acetone

Alkaloids
−
+
−
+

Flavonoids
+
+
+
+

Saponins
+
+
−
+

Phenolics
+
+
+
+

Tannins
−
−
+
−

Anthraquinones
+
−
−
+

Cardiac glycosides
+
+
+
+

Terpenoids
−
+
+
−

Steroids
−
+
−
−

Note: + = present, − = absent.

The weight of the leaf extracts and their yield obtained from different solvent extracts of L. camara are presented in Table 2. Different solvents showed a significant influence on the total dry weight and yield of the extracts. Relatively, the extract from methanol resulted in superior extraction yield (14.4%) with  μg of dry weight. The recovery of extractable constituents from different extracts remained in the following order of methanol > ethyl acetate > acetone > chloroform. Our results are in conformity with previous studies supporting the use of methanol as the best solvent to recover higher extractable compounds from various medicinal plants [23, 24]. Similarly, Anwar et al. [16] have stated that methanol as the best solvent for extraction from L. camara. Also, methanol was commonly employed by other researchers in L. camara for various biological studies [8, 25–27]. However, literature study shows that there are no available reports on the comparative yield analysis obtained from different solvent extracts till date. The existence of significant differences of dry weight of the extracts and yields between various organic solvents can be because of different polar nature of the solvents tested [24].

Table 2: Dry weight and total yield of different solvent extracts of L. camara leaves.

Solvent extracts
Weight of the extract (µg ± SD)
Yield (%)

Ethyl acetate
501.3 ± 3.5
10.0

Methanol
721.3 ± 1.5
14.4

Acetone
260.6 ± 4.0
5.2

Chloroform
141.6 ± 2.5
2.8

Note: each value is expressed as mean ± standard deviation (SD) (). Values in the column followed by a different letter superscript are significantly different ().

Polyphenols and flavonoids are the plant secondary metabolites occurring in several medicinal plants known to possess antimicrobial, antioxidant, antispasmodic, antidepressant, antitumor, antimutagenic, anti-inflammatory, and many other biological activities [27, 28]. In plants, these phenolic compounds provide defense against various pathogens, regulate cell division and growth, and help in pigmentation and many other metabolic pathways [29]. Therefore, we investigated the occurrence of total phenolic and flavonoid content in different organic solvent extracts (Table 3). The results clearly indicated the existence of statistically significant differences () among the different extracts. The highest phenolic content ( mg GAE/g) and flavonoid content ( mg RE/g) were observed in the methanol leaf extract of L. camara. On the other hand, ethyl acetate, acetone, and chloroform extract contained phenolic content of , , and  mg GAE/g, respectively. Total flavonoid content in ethyl acetate, acetone, and chloroform extract was found to be , , and  mg RE/g, respectively. Similarly, previous studies have shown the occurrence of rosmarinic and caffeic acid as the major phenolic compounds and few flavonoids such as 3,7-dimethoxy-, 3-methoxy-, and 3,7,4′-trimethoxyquercetin, hispidulin, 3, pectolinarigenin 7-O-β-D-glucoside, and camaraside glycoside were evident in the plant extract of L. camara [7, 11, 26]. Due to high polarity, methanol was found to exhibit better efficiency in extracting various polar phytocompounds (phenolics and flavonoids) from the leaves of L. camara. Both total phenolic and flavonoid contents obtained in our study were relatively much higher than the quantity obtained by earlier researchers in the same species but collected from geographically distant places [8, 16, 26]. However, total phenolic content was much lesser than the quantity ( mg gallic acid/g) as reported by Mahdi-Pour et al. [15] from methanol leaf extract of L. camara located in Kedah, Malaysia, and this difference can be attributed the influence of environmental factors and geographical location.

Table 3: Total phenolics and flavonoids content of different solvent extracts of L. camara leaves.

Solvent extracts
Total phenolic content
Flavonoid content

(mg GAE/g) ± SD
(mg RE/g) ± SD

Ethyl acetate
75.6 ± 0.9
16.7 ± 0.6

Methanol
92.8 ± 1.7
26.5 ± 0.5

Acetone
62.9 ± 1.7
20.6 ± 0.3

Chloroform
33.7 ± 0.5
21.2 ± 0.8

Note: each value is expressed as mean ± standard deviation (SD) (). Values in the column followed by a different letter superscript are significantly different () and values having the same letters are not statistically significant (). GAE: gallic acid equivalent, RE: rutin equivalent.

The formation of increased free radicals in human body may cause cell damage andinduces various disorders such as cancer, myocardial infarction, atherosclerosis, and neurodegenerative disorders. However, antioxidant compounds derived from natural source or plants can repair these free radicals formed in cells and thereby, antioxidants are very useful in preventing various disorders [2, 15, 23]. The antioxidant capacities of either natural products or crude plant extracts are usually evaluated by making use of DPPH radical scavenging test [23]. In principal, the test depends on the capacity of DPPH free radicals reacting with plant metabolites such as phenolic and flavonoid compounds (H⁺ donors) occurring in the sample. After the reaction, DPPH solution turns from purple to yellow color due to acquiring of a proton from the donor species. The intensity of color change directly relates to the scavenging ability of the biological sample [27]. Figure 1 shows the DPPH scavenging activity of L. camara leaf extracts in comparison to positive control (ascorbic acid). In all the solvent extracts, radical scavenging activity was found to be concentration dependent. The highest percentage of scavenging activity ( μg/mL) was observed in methanolic leaf extracts at 500 μg/mL concentration. The next best solvent extract was found to be acetone ( μg/mL) followed by ethyl acetate ( μg/mL) and chloroform ( μg/mL). However, the activities of all extracts were inferior to that of the ascorbic acid standard. The IC₅₀ values of DPPH free radical scavenging activity were found to be in the following order: ascorbic acid (80 μg/mL) > methanol extract (165 μg/mL) > ethyl acetate (200 μg/mL) > acetone (245 μg/mL) > chloroform (440 μg/mL). These results are on a par with or even superior to that of reports by other researchers on several other crude extracts of the plant evaluated under the same conditions using DPPH assay [27]. The higher antioxidant potential of plant extracts is correlated to the occurrence of many antioxidant compounds especially polyphenols [23]. Although the antioxidant activity of L. camara leaf extracts by using DPPH assay was reported by earlier researchers [15, 16, 26], none of them compared the effects of different solvents on antioxidant potential. In our study, due to higher solubility of antioxidant compounds, the methanol extract exhibited increased radical scavenging activity compared to other solvent extracts. Similarly, other researchers have stated that free radical scavenging potential of plant extracts depends mainly on the occurrence of bioactive compounds, particularly polyphenols [8, 30].

Figure 1: DPPH scavenging activities of various solvent extracts of L. camara.

In biological system, a large quantity of hydroxyl radicals is formed due to activation of immune cells which are known to be highly toxic radicals and causes extreme damage to all molecules occurring in live cells. These radicals can trigger cell toxicity and mutagenesis by damaging DNA nucleotides [8, 31]. Therefore, measuring hydroxyl radical scavenging activity can provide good information on the antioxidant potential of L. camara leaf extracts obtained by different solvents. The results of hydroxyl radicals inhibition obtained from our study are depicted in Figure 2. It is evident that, irrespective of the organic solvents used for extraction, the percent inhibition of hydroxyl radicals increased with the concentration of the extracts. At higher concentration of 500 μg/mL, the percentage of hydroxyl scavenging activity for ascorbic acid, ethyl acetate, methanol, acetone, and chloroform extracts was found to be , , , , and %, respectively. The IC₅₀ value was found to be in the following order of ascorbic acid (60 μg/mL) > methanol (110 μg/mL) > ethyl acetate (240 μg/mL) > acetone (300 μg/mL) > chloroform (510 μg/mL). The lower the IC₅₀ value, the higher the scavenging activity and hence, methanol extract was found to possess superior antioxidant potential compared to other extracts tested. However, their effect was considerably lesser than the standard, ascorbic acid. These results completely corroborate the earlier reports that have proved the existence of correlation between the antioxidant property and the concentration and composition of different plant metabolites occurring in the extracts [23, 32]. In our study, methanol extracts contained significantly higher quantity of phenolics ( mg GAE/g) and flavonoids ( mg RE/g) and hence possessed superior antioxidant potential compared to other solvent extracts.

Figure 2: H₂O₂ scavenging activities of various solvent extracts of L. camara.

At present, the increased prevalence of deadly diseases and microbes adapting to antibiotic resistance is a great concern in the medical world [33]. Hence, more research interest is shown by medical community towards the development or discovery of novel antimicrobial agents. Due to the severe side effects of several synthetic antibiotics, research preference is mainly focused on discovering plant based natural drugs [5, 34]. Since L. camara possessed numerous secondary metabolites, we evaluated the effects of their different solvent extracts against some common human pathogenic bacterial strains. The results of our study revealed that all solvent extracts of L. camara were effective against both Gram positive and Gram negative bacterial strains tested, but their efficacy varied (Table 4). With the increase in the concentration, there was an enhanced antibacterial activity irrespective of the solvent used for extraction. Gram negative bacteria were more susceptible to all extracts compared to Gram positive bacteria. In general, Gram negative bacteria are known to exhibit high resistance towards wide range of chemical agents and antibiotics compared to Gram positive bacteria. Besides, Gram negative bacteria are reported to be the most prevailing pathogens causing a large number of deaths [34, 35]. Thus, L. camara leaf extracts can be more beneficial in treating most of these Gram negative disease causing pathogens. Methanol extract had the highest inhibition activity against all the tested microbes when compared to any other solvent extracts. The methanol leaf extract exhibited the highest activity against E. coli ( mm) followed by K. pneumoniae ( mm) at higher concentration (10 μL/disc). S. aureus was also more vulnerable to methanol extract with  mm of inhibition zone at 10 μL/disc concentration. Among the tested bacterial strains, E. coli and B. subtilis showed increased zone of inhibition to all the solvent extracts and were the most susceptible strains. Ethyl extract was also most effective against B. subtilis while other bacterial strains were moderately inhibited. Likewise, acetone and chloroform extracts were also effective in inhibiting E. coli and B. subtilis. However, at lower concentrations, ethyl acetate extract showed no inhibition against S. aureus. In contrast, chloroform extract was less effective to all bacteria and at lower concentration, it failed to show antibacterial activity. L. camara finds its application in many parts of the world to cure various human ailments [7]. Previously, researchers have reported the varied antimicrobial potential of this plant and thus our reports support these findings [13, 14]. These results substantiate the findings of Naz and Bano [26] where methanol extract of L. camara leaves showed the highest antimicrobial activity. However, this is the first ever attempt which emphasizes the influence of different solvent extracts on human pathogenic bacterial strains. Our study clearly indicated the existence of considerable differences in the antibacterial activity among the various solvent extracts evaluated. This could be due to varied phytochemical constituents present in different solvent extracts.

Table 4: Antibacterial activity of different solvent extracts of L. camara at different concentrations.

Solvent extracts (µL/disc)
Zone of inhibition (mm)

Escherichia coli
Klebsiella pneumoniae
Micrococcus luteus
Bacillus subtilis
Staphylococcus aureus

Ethyl acetate

    2.5
08.2 ± 0.8
06.9 ± 0.5
06.1 ± 0.7
10.0 ± 0.5
—

    5.0
13.0 ± 0.9
08.3 ± 0.5
07.1 ± 0.3
13.8 ± 0.5
06.1 ± 0.1

    10.0
12.0 ± 0.5
10.5 ± 0.8
07.0 ± 0.5
13.9 ± 0.4
10.6 ± 0.4

Methanol

    2.5
14.6 ± 0.5
08.2 ± 0.3
08.1 ± 0.7
10.0 ± 0.3
14.1 ± 0.2

    5.0
18.2 ± 0.2
14.5 ± 0.5
12.2 ± 0.3
14.0 ± 0.6
16.1 ± 0.6

    10.0
24.1 ± 0.4
18.1 ± 0.4
18.0 ± 0.5
16.1 ± 0.2
18.0 ± 0.4

Acetone

    2.5
16.1 ± 0.4
06.1 ± 0.6
07.9 ± 0.2
14.2 ± 0.3
05.8 ± 0.6

    5.0
24.0 ± 0.4
10.1 ± 0.6
12.3 ± 0.2
15.9 ± 0.4
10.2 ± 0.2

    10.0
28.2 ± 0.6
16.2 ± 0.2
12.2 ± 0.2
16.3 ± 0.4
12.2 ± 0.4

Chloroform

    2.5
10.6 ± 0.6
—
—
10.5 ± 0.9
—

    5.0
12.9 ± 0.6
09.2 ± 0.2
06.8 ± 0.7
12.1 ± 0.7
07.2 ± 0.2

    10.0
14.8 ± 0.3
11.4 ± 0.8
08.2 ± 0.2
12.4 ± 0.4
07.9 ± 0.2

Note: the negative control discs were soaked with 50 μL DMSO and the positive control discs with 50 μL (50 μg/mL) chloramphenicol. Each value represents the mean ± standard deviation (SD) of 3 replicates per treatment in 3 repeated experiments. “—” represents no activity.

Further, we used GC-MS analysis to identify the bioactive compounds occurring in the most competent solvent extract of L. camara. GC-MS profiling was performed only for methanolic leaf extract due to the fact that it contained many phytochemicals and exhibited superior biological activities. The distinctive chromatogram of the methanolic leaf extract of L. camara is shown in Figure 3. The analysis separated and identified a total of 32 known compounds belonging to different chemical classes (Table 5). The major compounds included hexadecanoic acid (5.197%), phytol (4.528%), caryophyllene oxide (4.605%), 9,12,15-octadecatrienoic acid, methyl ester, (Z,Z,Z)- (3.751%), 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (2.954%), α-D-galactopyranoside, methyl (2.790%), coumaran (2.288%), germacrene-D (2.185%), bicyclo[5.2.0]nonane, 2-methylene-4,8,8-trimethyl (2.065%), spathulenol (1.888%), 1,2,3-propanetriol, 1-acetate (1.689%), propane-1,2,3-triol (1.1615), and 2,4(1H,3H)-pyrimidinedione, 5-methyl- (1.180%). Few other compounds identified in the extract are α-elemol, myristic acid, neophytadiene, furfuryl alcohol, propargyl alcohol, and acetic acid, fluoro-, ethyl ester. Many of these identified constituents are known to possess several pharmacological activities. Hexadecanoic acid, a major phytoconstituent of L. camara methanolic leaf extract, is known to possess strong antimicrobial activity [36]. The diterpene, phytol, is an important compound reported with antioxidant, cytotoxic, and antimicrobial properties [37]. Similarly a conjugated saponin, 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one, is reported to possess strong antioxidant, anticancer, and anti-inflammatory properties [38, 39]. Caryophyllene oxide, spathulenol, and germacrene-D are known to possess anticarcinogenic, anti-inflammatory, and antibacterial properties [2, 40]. As a biofumigant, coumaran is reported to act against insect pests found in stored food grains [41]. The compound 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one has been reported in plant extracts exhibiting antioxidant, antiproliferative, and anti-inflammatory properties [40]. More recently, anti-inflammatory and cytotoxicity activities of hexadecanoic acid, methyl ester have been reported by Othman et al. [42]. However, pharmacological activities of other compounds of L. camara methanolic leaf extract are yet to be determined. Therefore, we assume that the strong bioactivities exhibited by L. camara in this study are correlated to the occurrence of these bioactive compounds in the methanol solvent extract. However, further studies on the isolation, characterization, and biological evaluation of these identified compounds are necessary to confirm their potential benefits.

Table 5: The major phytocompounds detected in the methanolic leaf extract of L. camara by GC-MS analysis.

S. number
Name of the compound
Peak number
Retention time (min)
Area (%)

1
2-Propanone, 1-hydroxy-
1
2.703
0.481

2
Propane-1,2,3-triol
3
3.275
1.161

3
Propargyl alcohol
4
3.653
0.877

4
Acetic acid, fluoro-, ethyl ester
5
3.719
0.737

5
Furfuryl alcohol
7
5.672
0.750

6
2,4(1H,3H)-Pyrimidinedione, 5-methyl-
9
14.366
1.180

7
2,3-Dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one
11
17.443
2.954

8
Coumaran
12
21.251
2.288

9
1,2,3-Propanetriol, 1-acetate
13
22.529
1.689

10
Cyclohexasiloxane, dodecamethyl-
14
23.200
0.978

11
4-Vinylguaiacol
15
25.393
0.809

12
Bicyclo[5.2.0]nonane, 2-methylene-4,8,8-trimethyl
19
29.798
2.065

13
Germacrene-D
21
32.547
2.185

14
Longifolene
22
33.22
0.889

15
4-Epi-cubedol
23
34.084
0.817

16
Caryophyllene oxide
25
36.995
4.605

17
α-D-Galactopyranoside, methyl
26
37.909
2.790

18
Humulene epoxide II
27
38.173
0.696

19
Spathulenol
30
38.886
1.888

20
α-Elemol
34
39.997
0.507

21
Myristic acid
42
43.751
0.652

22
Neophytadiene
45
46.059
0.820

23
3-Eicosyne
53
47.594
0.211

24
9-Octadecenoic acid (Z)-, methyl ester
60
49.296
0.093

25
Hexadecanoic acid, methyl ester
61
49.438
0.696

26
Hexadecanoic acid
63
50.888
5.197

27
9,12-Octadecadienoic acid (Z,Z)-, methyl ester
65
55.007
1.037

28
9,12,15-Octadecatrienoic acid, methyl ester, (Z,Z,Z)-
66
55.225
3.751

29
Phytol
67
55.426
4.528

30
Octadecanoic acid, methyl ester
68
56.428
0.330

31
9,12,15-Octadecatrienoic acid, (Z,Z,Z)-
70
56.640
1.019

32
Phthalic acid, di(2-propylpentyl) ester
74
67.804
0.688

Peak number is represented in Figure 3.

Figure 3: GC-MS chromatograph of methanolic leaf extract of L. camara.

4. Conclusion

In conclusion, the present investigation clearly revealed that phytochemical composition of L. camara leaf extract varied with respect to different solvents. Total phenolic and flavonoid content significantly varied among the different solvent extracts. Methanol solvent extract of L. camara leaves contained more extractable metabolites compared to any other solvents. Moreover, all solvent extracts of L. camara showed considerable antioxidant and antimicrobial activity with varying differences due to differences in their phytochemical composition. Thus, our study suggests that methanol leaf extract of L. camara containing many bioactive compounds may possibly be utilized as a therapeutical source for developing beneficial drugs to manage various human diseases and disorders.

Disclosure

Mohd. Sayeed Akhtar is a coauthor.

Conflict of Interests

The authors declare that there is no conflict of interests.

Acknowledgments

The authors are highly grateful to the Department of Crop Science, Universiti Putra Malaysia, Malaysia, for providing research facilities and the Department of Biosciences, Universiti Putra Malaysia, Malaysia, for GC-MS analysis.

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