Evaluation of Antimicrobial Activity, Cytotoxicity, and Phytochemical Composition of Ocimum americanum L. (Lamiaceae)

Abstract

Background. Herbal plants are a natural source of novel biomolecules used widely in ethnomedicine. The present study was intended to examine the antimicrobial properties, cytotoxicity, and phytoconstituents of Ocimum americanum L., an herb traditionally used by the people of Swahili (Kenya) against microbial infections. Methods. The aerial parts of Ocimum americanum L. were sourced, dried, milled, and extracted using three solvents: aqueous, acetonic, and 70% hydroethanolic. Additionally, fractions of chloroform and ethyl acetate were obtained from all crude extracts of the plant. The antimicrobial property was evaluated using agar well diffusion and microdilution techniques against human opportunistic pathogens including S. aureus, E. coli, and C. albicans. The brine shrimp cytotoxicity test was used to analyze the lethality of the extracts and fractions. Phytochemical screening was used to qualitatively assay the presence of phytoconstituents. Results. The phytochemical assay confirmed the presence of alkaloids, phenols, flavonoids, tannins, saponins, terpenoids, reducing sugars, anthraquinones, and glycosides. The lethality test demonstrated that all the extracts and fractions were toxic against Artemia salina nauplii with LC50 values ranging from 0.59 to 559.71 µg/ml. Chloroformic fraction of the hydroethanolic extract had the highest lethality with an LC50 value of 0.59 µg/ml. Two of the extracts and their fractions displayed antimicrobial activity against the Gram-positive bacteria (B. cereus and S. aureus) and fungus (C. albicans), while the same extracts had no activity against the Gram-negative bacteria (E. coli and K. pneumoniae). The highest antimicrobial activity was seen in the ethyl acetate fraction of the hydroethanolic extract at 250 mg/ml against Bacillus cereus which had an inhibition zone of 26.00 ± 0.00 and MIC value of 62.5 mg/ml. Conclusion. In the current study, we report that Ocimum americanum L. demonstrated moderate antimicrobial activity, contains numerous phytocompounds, and is highly cytotoxic; thus, further research is needed for bioprospecting a novel compound.

Ocimum basilicum and Ocimum americanum: A Systematic Literature Review on Chemical Compositions and Antimicrobial Properties

“…The hydroethanolic extract's ethyl acetate fraction, at 250 mg/ml demonstrated the highest antibacterial activity against B. cereus , with an inhibition zone of 26.00 ± 0.00 and a minimum inhibitory concentration of 62.5 mg/ml. 94…”

“…The specific bacterial and fungal strains of Salmonella enterica , Candida albicans , C. tropicalis , Staphylococcus aureus , and Serovar typhimurium were all suppressed by the extracts. 77 Based on Ali et al, 94 crude extracts of Ocimum americanum demonstrated toxicity against artemia salina nauplii as it investigated biogenic zinc oxide nanoparticles synthesized using Ocimum americanum plant extract for antimicrobial and cytotoxicity effects of bacillus cereus, Klebsiella pneumonia, S. aureus , E. coli , S. aureus , and C. albicans . Reports by Dharsono and his coworkers 44 detail the antimicrobial activity of certain essential oils against Streptococcus species obtained from pigs, along with the minimum inhibitory concentration of an antibacterial test used to assess the oils’ inhibitory power.…”

“…The hydroethanolic extract's ethyl acetate fraction, at 250 mg/ml demonstrated the highest antibacterial activity against B. cereus, with an inhibition zone of 26.00 ± 0.00 and a minimum inhibitory concentration of 62.5 mg/ml. 94 According to Sadegh Kiani, 97 because of its highest richness in secondary metabolite bioactive medicinal plants, Ocimum basilicum, also known as great basil, is used in various areas of pharmaceutical activity, including antioxidants, antiosteoporotic, anxiolytic and tranquilizers, anti-Colitis, antibacterial, and cytotoxic effects; it is also used in cardiovascular disease, antihepatotoxicity, phyto-remediatory, hypoglycemic, antihypertensive, and anti-inflammatory properties. 98,99 Limitations.…”

Phytochemical Screening and Antimicrobial Activity Evaluation of Selected Medicinal Plants in Ethiopia

“…Each fraction of the plant extracts were then concentrated using rotary evaporator; scanted and dried by putting it in warm mental mantle using desiccator to remove the solvent residue based on previous studies. [22][23][24][25] Thin Layer Chromatography (TLC) Test Thin layer chromatography was performed on TLC plate (aluminum silica gel pre-coated with layer thickness of 0.2 mm) using hexane/ethyl acetate mixtures (8:2) as an eluent. Spots were applied using capillary tube 1.5 cm from the bottom marked by a line ruled using a pin.…”

Comparative Morpho-micrometric Investigations in Six Indigenous Ocimum Species of India with DOE Based HPTLC Method for Multi-class Component Analysis

“…The O. filamentosum is an understudied species in the genus possibly because it is less aromatic than the rest of the species; however, it has been reported to have microbicidal properties [14,15]. Ocimum species are rich source of phenolic compounds and in vitro analysis of their extracts shows potent anti-inflammatory, antioxidant, and antimicrobial activities thus justifying its adaptogenic use in an array of health conditions [16][17][18]. They are also commercially utilized in the form of bioactive volatiles-containing essential oils yielded from the plants for its various biological activities [19,20].…”