In vitro and In silico evaluation of antioxidant potential and phytochemical quantification of Plectranthus amboinicus (Lour.) Spreng roots

Abstract

Plectranthus amboinicus (Lour.) Spreng is a medicinal plant that belongs to the family Lamiacea and is known for its diverse pharmacological properties. Though the various parts of the plant have been extensively studied, roots remain less explored. This research aimed to evaluate phytochemical and antioxidant activities of P. amboinicus roots using in vitro and in silico methods. Different plant extracts of roots were made using sequential cold maceration method with n-Hexane, Chloroform and Methanol. Total Phenolic Content (TPC), Total Flavonoid Content (TFC) and Total Antioxidant Capacity (TAC) were determined while the antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Gass Chromatography-Mass Spectrophotometry (GC-MS) analysis was performed to identify the phytochemicals present in the root extracts. The identified phytochemicals were subjected to in silico molecular docking study with Superoxide dismutase (SOD) enzyme to simulate binding affinities by using GOLD Suite software. Docking results were compared and analyzed with the standard ligand binding capacity with SOD enzyme. The n-Hexane extract showed the highest TPC (28.22 ± 1.155 mg GAE/g), whereas the Methanol extract showed the highest TFC (21.78 ± 0.254 mg QE/g). The TAC assay indicated n-Hexane extract showed the highest antioxidant capacity (7.3490 ± 0.446 mg AAE/g). Nevertheless, the Methanol extract showed the best scavenging activity with the lowest IC50 of 78 ± 1.194 μg/mL while the standard Ascorbic acid showed IC50 of 148.5 ± 0.333 μg/mL. Palmitic acid (C16H32O2), Aromadendrene (C15H24), and Hexanedioic acid (C6H10O4) were identified as the most abundant compounds present in extracts via GC-MS. Palmitic acid-SOD interaction showed a high binding potential with 3 Hydrogen bonds and 59.1739 of PLP fitness score while the standard Ascorbic acid-SOD showed only 44.496 of PLP fitness score. The study highlights the significant antioxidant potential of P. amboinicus root extracts. The Methanol extract exhibited the highest free radical scavenging activity, while Palmitic acid showed strong binding affinity with the Superoxide dismutase enzyme. These findings indicate that P. amboinicus roots possess considerable potential as a natural source of antioxidant agents. The results can be applied in the development of herbal supplements, functional foods, skincare products, and antioxidant-based therapies.