Exploring of Chemical Profile and Biological Activities of Three Ocimum Species From Comoros Islands: A Combination of In Vitro and In Silico Insights

Abstract

Ocimum species have a great interest in different traditional medicinal systems. This study examined the chemical composition, antioxidant properties, enzyme inhibitory effects, and antibacterial and antifungal activities of the aerial parts of Ocimum gratissimum, Ocimum americanum, and Ocimum basilicum from the Comoros Islands. The extracts were analyzed using high-performance liquid chromatography-mass spectrometry (HPLC-MS) to determine their chemical composition. Antioxidant activity was assessed using 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), chelating ability, and phosphomolybdenum radical scavenging assays. Enzyme inhibitory activities against acetylcholinesterase (AChE), butrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase were evaluated using spectrophotometric methods. Antibacterial and antifungal activities were tested using the broth microdilution method against selected pathogenic microorganisms. The selected enzymes and proteins were evaluated using in silico methods with biomolecules from these plants. In addition, 111 different metabolites were identified in the tested extracts using advanced HPLC/MS techniques. The most significant number of detected compounds were derivatives of hydroxycinnamic acids, followed by flavonoid glycosides and aglycones and derivatives of hydroxybenzoic acids. All three Ocimum species exhibited significant antioxidant activities, O. gratissimum exhibited the best-reducing abilities in CUPRAC and FRAP assays. In addition, enzyme inhibitory assays revealed that O. americanum had the most potent inhibitory effect on tyrosinase (48.01 ± 3.89 mg kojic acid equivalent [KAE]/g), and amylase (1.08 ± 0.02 mmol acarbose equivalent [ACAE]/g). Antibacterial and antifungal tests demonstrated that the extracts possess broad-spectrum activity. Molecular docking results showed that compounds exhibited remarkable binding energies with target enzymes and proteins. The molecular dynamics simulations identified chicoric acid with MurE of Staphylococcus aureus complex as the most promising drug candidate. These findings support their traditional medical and nutraceutical uses and suggest possibilities for natural functional applications.

Keywords: Ocimum species; antimicrobial effects; antioxidant properties; chemical profile; chicoric acid; in silico.