Introduction

The Scutellaria, belonging to Lamiaceae family, includes nearly 350 species. Being anti-inflammatory, antioxidant,sedative, antiviral and antithrombotic, some Scutellaria species are widely used in traditional medicine in Asian countries, especially in China, Korea, and Japan [1]. Twenty Scutellaria species including S. fragillima, S. xylorrhiza, S. farsistanica, S. luteo-coerulae, S. glechomoides, S. nepetifolia, S. theobromina and S. persica as an endemic species currently exist in Iran [2]. Phytochemicals, the secondary metabolites, are the outcome of secondary metabolism in the plant, which are created for defenses and used for determination of taxonomy of plant species. Thus, evaluating the compositions of medicinal plants is a measure for the biological activities of medical plants. Thus, phytochemicals represent the biological activity of medical plants. Natural products have been the source of most of the active ingredients of medicines and drug discovery using natural products is a challenging task for designing new leads [3-6]. Scutellaria is a source of biological active compounds such as volatile oils, flavonoids, phenolic compounds, dihydropyrano coumarins, polyhydroxy flavonoids, stilbenes, terpenoids, phenethyl alcohol glycosides, and polysaccharides [7-15]. It is indicated that flavonoids and terpenoids extracted from Scutellaria show insect antifeedant, cytotoxic and anticancer activity [16-18]. Extracts and volatile oils of Scutellaria species had antimicrobial, antioxidant and phytotoxic activity. Linalool, (E)-caryophyllene, germacrene D and caryophyllene oxide are the most volatile oil constituents [19-21]. The goal of this study is to evaluate the medical effect of chemical constituents, antioxidant and antibacterial activity of essential oil and methanolic extract of the aerial part of S. condensata subspeices pycnotricha. According to the impact of chemotaxonomy on prediction the biological activity of medicinal species, the diversity on essential oil composition of Scutellaria species was reviewed.          

Experimental

Plant material condensata subspieces pycnotricha (Boshghabi, Persian name) was founded in Northwest of Sanandaj, Kurdistan Province, Iran, at an altitude of 2400 m in July 2016 (flower stage) and botanist Hossein Maroofi (voucher specimen no 13340) confirmed it in the herbarium of the Institute of Forests and Rangelands Researches, Sanandaj, Iran.

Isolation of essential oil

The air-dried sample of essential oil (120 g) was extracted by hydrodistillation. This process that lasted 4 hours, was completed by Clevenger-type apparatus. The volatile oil was dried by (Na₂SO₄) and held in the closed dark vial at 4 °C before the analysis.

GC and GC/MS analyses

Volatile oil was analyzed qualitatively and quantitatively by GC/Mass and GC/FID. GC/FID was used as an optimum separation method. The injection of the diluted volatile oil in chloroform to Thermoquest GC/FID was done by DB-5 column (60 m × 0.25 mm), so that the temperature of injector was 250 °C, and that of detector was 300 °C. The nitrogen with a flow rate of 1 mL/min was used as carrier gas. The oven temperature was between 60 to 250 °C at the rate of 5 °C/min. At last, it was held for 2 min in isothermal elution situation. Carrier gas Helium was used for GC/MS (Thermoquest-TRACE) and ionization voltage was at 70eV. The mass range in detector was from 43 to 456 m/z. The injection of a mixture of normal alkanes including C₆-C₃₀ to GC/FID was done as method of volatile oil for determination of experimental retention index of compounds. The constituent of volatile oil was specified based on factors such as comparing the mass spectra by a library (Adams and Wiley), retention index and retention time, then the quantity of specified constituents was determined by relative area percentage of GC/FID (without correction factors) [22].

Preparation of the extract

The maceration methods were used for the methanolic extract of S. condensata subsp. pycnotricha (200 g) for 72 h triplicate in room temperature. The extract was concentrated by a rotary evaporator in 50 °C and reserved in 4 °C.

Phytochemical screening

Qualitative identification of the constituents of S. condensata subsp. pycnotricha methanolic extract was carried out using the procedures that explained by Kumar Bargah [23].

Measurement of free radical-scavenging activities (DPPH assay)

The capacity of S. condensata subsp. pycnotricha essential oil and methanolic extract to scavenge DPPH was specified based on the technique reported by Euch et al. [24]. The absorbance of the mixture containing sample and reagent was measured at 517 nm and BHT was used as a control for its compurgation. Quantification of free radical-scavenging activity of the sample was carried out according to the evaluation of the IC₅₀ (sample concentration providing 50% inhibition), by plotting the inhibition percentage against sample concentrations.

Determination of total phenolics content

The Folin–Ciocalteu procedure defined the total phenolics content (TPC) of the S. condensata subsp. pycnotricha extract [25]. Total phenolic content was reported as milligram gallic acid equivalents per gram of plant extract (mg (GAE)/g).

Determination of total flavonoid

Total flavonoid content of the methanolic extract of S. condensata subsp. pycnotricha was determined based on the method reported by Ghasemzadeh et al. [26]. The absorbance of mixture solution was measured to be 430 nm by spectrophotometer. Then, quercetin flavonoid was used to plot a standard curve and the result was represented in mg quercetin/g dry weight.

Antibacterial activities

An experiment was done on essential oil of S. condensata subsp. pycnotricha against 9 bacteria, including Bacillus cereus PTCC1015 (Persian Type Culture Collection number), Escherichia coli ATCC25922 (American Type Culture Collection number), Staphylococcus aureus ATCC 25923, Klebsiella pneumoniae ATCC10031, Bacillus subtilis ATCC 465, Pseudomonas aeruginosa ATCC85327, Bacillus pumilus PTCC1274, Staphylococcus epidermidis ATCC12228, and Enterococcus faecalis ATCC 29737. The antibacterial activity of essential oil was specified by the disk diffusion method and using Mueller–Hinton Agar plates, then, the results were expressed as inhibition zones. Meanwhile, the MIC values were reported by the broth microdilution assay [27].

Results and Discussioncondensate has two subspecies in Iran: S. condensata Rech.f. ssp. condensate and S. condensata Rech.f. ssp. pycnotricha, but no study on them is available. Kurdistan Province, in the west of Iran, is an appropriate place for finding medicinal plants and introducing their traditional medicine. According to a dry weight of plant and using hydrodistillation method, the yellow essential oil of S. condensata subsp. pycnotricha by 0.4% yield (w/w%) was obtained from Clevenger apparatus. The 96.47% of S. condensata subsp. pycnotricha essential oil constituents were determined by examination of GC/Ms and GC/FID spectrum. Based on GC/Ms spectrum, thirty-two compounds were recognized and GC/FID was used to examine their quantity. The S. condensata subsp. pycnotricha compounds were listed in Table 1 which is based on the retention time of in DB-5 column. Linalool (25.3%), carvacrol (16.26%), (E)-caryophyllene (13.43%), α-terpineol (5.03%), geraniol (4.86%) and caryophylla-4(12), 8(13)-dien-5α-ol (4.08%) were the major compounds. The oxygenated monoterpenes (37.03%), includeding Linalool, α-terpineol and geraniol, were the main compounds in S. condensate essential oil. There was not any monoterpene hydrocarbon in the essential oil (Figures 1, 2, and 3)

Table 1. Chemical composition of the essential oils of S. condensata subsp. pycnotricha

^aRI: retention indices relative to C₆-C₂₄ n-alkanes.

^bRI: retention indices from literature (DB-5 column)

Figure 1. The structure of major compounds from S. condensata subsp. pycnotricha essential oil

Figure 2. GC-MS chromatogram of S. condensata subsp. pycnotricha essential oil

Figure 3. Mass spectra of S. condensata subsp. pycnotricha essential oil major constituents

Given to the same metabolism pathway in different species and chemotaxonomy, we can use comparison of essential oil compounds of Scutellaria in the taxonomy of Scutellaria genus. This comparison is useful in the prediction of species biological activity. In Table 2, you can find the major compounds, extraction method and biological activity of Scutellaria species’ essential oils.

Table 2. Volatile oil compounds of Scutellaria species

It is reported that according to preliminary phytochemical tests, the secondary metabolite in methanolic extract of S. condensata subsp. pycnotricha were phenolic, tannin, saponin, flavonoid, phlobatannin and steroids (Table 3). Investigations indicated that flavonoids, tannins, saponins, alkaloids, coumarins and steroids were the main secondary metabolite of Scutellaria species. As the result of such examination, the phenolic compounds were the major secondary metabolite of Scutellaria species. It is also revealed that the  antioxidant activity of the plant was due to the phenolic compounds [28]. So, free radical scavenging capacities of essential oil and methanolic extract of S. condensata subsp. pycnotricha were measured by DPPH assay (Table 4). As a result, the highest scavenging activity belonged to methanolic extract (IC₅₀₌ 38.2 µg/mL), followed by essential oil (IC₅₀₌ 93.2 µg/mL), compared with BHT as a positive control (IC₅₀₌ 24.0 µg/mL). According to the spectrophotometer results, the total phenolic and total flavonoid content of methanolic extract of S. condensata were 120.7 mg GAE/g sample and 78.6 mg QE/g sample, respectively (Table 4). The high antioxidant activity of methanol extract of S. condensata subsp. pycnotricha was related to its phenolic content. The essential oil of S. condensata subsp. pycnotricha was tested against four Gram-negative and five Gram-positive bacteria. As a result, the essential oil showed moderate to high inhibitory activity against the Bacillus cereus, Escherichia coli, Staphylococcus epidermidis and Bacillus pumilus (Table 5)

Table 3. Preliminary phytochemical screening of S. condensata subsp. pycnotricha methanolic extract

⁺ Presence; ^-Absence

Table 4. Antioxidant activity, total phenolic content and total flavonoid content of the essential oil and methanolic extract of S. condensata subsp. pycnotricha

Values were the means of three replicates ± standard deviation

Table 5. In vitro antibacterial activity of S. condensata subsp. pycnotricha essential oil

^aZone of inhibition (in mm) includes diameter of the disc (6 mm), ^bMinimum inhibitory concentration values as mg mL^–1, (–): Inactive, (7 – 13): moderately active, (> 14): highly active, nt: not tested, ^cTested at 30 μg/disc, ^dTested at 10 μg/disc, e: Tested at 10 μg/disc

Conclusion

The present study is the first one on the phytochemical analysis as well as antioxidant and antibacterial activities of S. condensata subsp. pycnotricha essential oil and extract. The study on volatile oil compounds of Scutellaria genus can be used for the further study on the taxonomy of Scutellaria genus and their biological activity prediction. The high antioxidant activity and the medium antibacterial inhibitory effect of the S. condensata subsp. pycnotricha indicate its potential for being a prospective antioxidant and antibacterial source in pharmaceutical and food industries.

Acknowledgements

We are grateful to Vice-chancellor for Research and Technology, Hamadan University of Medical Sciences (Grant No. 9905073021) for financial support of this work.

Citation F. Ismail Ahmadi, R. Fathollahi, D. Dastan*. Phytochemical Constituents and Biological Properties of Scutellaria Condensata Subsp. Pycnotricha. J. Appl. Organomet. Chem., 2022, 2(3), 119-128.

          https://doi.org/10.22034/jaoc.2022.154719

Copyright © 2022 by SPC (Sami Publishing Company) + is an open access article distributed under the Creative Commons Attribution License(CC BY)  license  (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.