Accurate certification and studies of phytoconstituents are increasing periodically, as they are repositories of several potent drugs. Gas chromatography and mass spectroscopy (GC–MS) has been validated to be a significant tool for bioprospecting of plant bioactive compounds. However, diethyl phthalate and n-hexadecanoic acid were identified to be common in leaf and root extract of S. khasianum. Other organic compounds in leaf extract that are accountable for their wide use in medicinal aid include: Dodecanal, reported to possess highest antibacterial activity (Faridha Begum et al. 2016). Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,octadecyl ester shows strong antifungal and antioxidant activities in Azadirachta and Thesium humile (Akpuaka et al. 2013; Belakhdar et al. 2015).
The remaining bioactive compounds analyzed were as follows: Diethyl phthalate, a phytoconstituent well known for its antimicrobial, antioxidant, plasticizer and estrogenic activities in Ceropegia bulbosa Roxb (Arora and Meena 2017). E-9-Tetradecenoic acid is reported to have analgesic, anti-inflammatory and antioxidant properties in Cassia angustifolia (Al-Marzoqi et al. 2016). The bioactive compound, Myristoleic acid reported in Sesame Seeds was known to prevent cancer (Bhatnagar and Gopala Krishna 2009).
The bioactive molecule n-Hexadecanoic acid has reported to have multiple biological properties in Vitex negundo (Kumar et al. 2019; Enerijiofi et al. 2021). The phytol, a bioactive compound reported earlier in several species like Hydrilla verticillate, Gracilaria edulis and Carissa carandas with diversified medicinal uses (Prabha et al. 2019; Rao et al. 2019). The compound 9,12,15-Octadecatrienoic acid was known to possess several biological properties like analgesic, anesthetic, anticonvulsant, anti-inflammatory, antioxidant, anti-pyretic, antibacterial (Kalaivani et al. 2012); anticancer, antihistaminic, hepatoprotective, hypocholesterolemic, nematicide (Rao et al. 2019) in Andrographis paniculata and Carissa carandas and also known to reduce complications in Covid-19 patients (Weill et al. 2020). α-d-Glucopyranoside, O-α-d-glucopyranosyl-β-d-fructofuranosyl, a phytochemical compound also found in Cyperus alternifolius have cardioprotective, neuroprotective, antidiabetic, antiosteoporotic, anti-inflammatory and antistress properties (Al-Gara et al. 2019). The 1,2-Propanediol, 3-(tetradecyloxy), a phytoconstituent reported to have antifungal activity (Sundberg and Faergemann, 2008), whereas the compound tert-Hexadecanethiol was known for its antitumor activity in Malaxis acuminta (Raval et al. 2016); antioxidant, antifungal and insecticidal activities in Capsicum annuum (Sathya et al. 2016). Another bioactive molecule Heptadecane, 9-hexyl (Fig. 2), the major bioactive compound of S. khasianum leaf extract, known to possess strong antifungal activity in Senecio coluhuapiensis (Arancibia et al. 2016). The compound Myoinositol, hexaacetate acts as a precursor of several metabolic pathways, co-factors for enzymes and as messenger molecule in signal transduction (Chhetri, 2019; Kim et al. 2008). The biological activity of some compounds has not yet identified (Table 1).
The chemical profiling of root methanolic extracts of S. khasianum identified different bioactive compounds. Among them, more predominant compound identified was stigmasterol, known to possess anti-inflammatory, antioxidant, antimicrobial and sedative activities (Al-Rubaye et al. 2017). The initial compound eluted was 2-Pyrrolidinone, 1-methyl with anticancer, antioxidant, antibacterial, antifungal, anticonvulsant and surfactant properties (Hosseinzadeh et al. 2017). The other bioactive compounds identified were as follows: 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl, a ketone reported earlier in Malva sylvestris, known to possess several biological properties (Al-Rubaye et al. 2017; Ashwathanarayana and Naika, 2017). 2-Methoxy-4-vinylphenol, a phytoconstituent with antioxidant, antimicrobial, anti-inflammatory properties in Cassia angustifolia (Alghamdi et al. 2018). The compound, Eugenol, has several biological properties like antioxidant, antimicrobial (Hamed et al. 2012), anti-proliferative and anti-inflammatory activities (Fujisawa and Murakami 2016).
The bioactive compound Benzaldehyde, 3-hydroxy-4-methoxy, which is known for its antimicrobial activity and inhibits enzymes like 17-β-hydroxysteroid dehydrogenase, testosterone hydroxylase and arylamine-N-acetyltransferase (Prabhu et al. 2020). 1,3-Propanediol, 2-ethyl-2-(hydroxymethyl), is one such bioactive molecule with antioxidant and antimicrobial activity in Erythrina variegata (Umarani and Nethaji 2021). Ethanone, 1-(4-hydroxy-3-methoxyphenyl) and Ethanone, 1-(4-hydroxy-3,5-dimethoxyphenyl) were the two identified non-steroidal bioactive compounds reported to have anti-inflammatory, antioxidant, enzyme inhibitor properties and also employed as food additive (Ashwathanarayana and Naika 2017). The compound 4-((1E)-3-Hydroxy-1-propenyl)-2-methoxyphenol, has been reported to have diverse biological activities like antimicrobial, antioxidant, anti-inflammatory and analgesic (Mostafa et al. 2020). Tetradecanoic acid was identified as a cancer preventive, antioxidant, nematicide, lubricant and hypocholesterolemic in Ceropegia bulbosa (Arora and Meena 2017). Solavetivone, a phytoconstituent of tobacco and Solanum erianthum, has fungitoxic, antimicrobial and weak cytotoxic activities (Chen et al. 2013). Similarly, a compound phthalic acid, isobutyl nonyl ester was observed to be efficient in curing persistent cardiac and cerebrovascular problems, cancer, inflammation and bacterial infections (Ma et al. 2015). The compound 9,12-Octadecadienoic acid (Z,Z) was known to possess anticarcinogenic, antioxidant, anti-inflammatory and antiatherogenic properties (Arora and Meena 2017).
The second highest compound, cis-vaccenic acid, was well known for its anti-carcinogenic effect in Origanum vulgare (Al-Tameme et al. 2015). Similarly, geranylgeraniol (Ho et al. 2018) and vitamin E (Arora et al. 2017) were reported to have several biological properties. The compound 9,10-Secocholesta-5,7,10(19)-triene-3,24,25-triol, (3β,5Z,7E), acts as biocide and anti-corrosion agent in Piper nigrum (Mohammed et al. 2016). Spirost-8-en-11-one, 3-hydroxy, -(3β,5α,14β,20β,22β,25R) was found to possess anticancer (Rajendran et al. 2017), estrogenic, progesterogenic and anti-inflammatory effects (Gopu et al. 2021). Among the bioactive compounds identified in the root methanolic extracts of S. khasianum, the biological activity of some compounds was not yet identified and reported (Table 2).
The S. khasianum leaf methanolic extracts showed high antibacterial activity against P. aeruginosa in concentration-dependent manner, followed by E. coli, B. sphaericus and S. aureus (Fig. 3), whereas the root methanolic extract exhibited high antibacterial activity against E. coli, followed by P. aeruginosa, S. aureus and B. sphaericus. The result indicates that the S. khasianum root extract exhibited remarkable antibacterial property against P. aeruginosa and E. coli. Therefore, root methanolic extract of S. khasianum was considered as the most effective extract than leaf extract with regard to high anti-bacterial activity (Pavani and Shasthree 2021). This indicates that the root extract had more antibacterial compounds than leaf extract. Our results were in accordance with the reports on Momordica cymbalaria (Chaitanya and Pavani 2021). This study confirms that the S. khasianum extracts have significant antibacterial activity against tested bacteria.