Polyphenolics content and biological activity of Plectranthus amboinicus (Lour.) spreng growing in Egypt (Lamiaceae)

Background: Volatile oil, terpenoids, mainly diterpene and polyphenolic compounds including flavonoids and phenolic acids were previously isolated from different Plectranthus species. Plectranthus amboinicus (Lour.) Spreng growing abroad was subjected to phytochemical study resulted in isolation of several flavonoids, also the plant exhibited antioxidant, diuretic, anti-inflammatory, cytotoxic and antimicrobial activities. Materials and Methods: In this study ethyl acetate fraction of Plectranthus amboinicus (Lour.) Spreng leaves growing in Egypt was fractionated and chromatographed on silica gel and sephadex to isolate its phenolic constituents. The isolated compounds were identified using UV, 1HNMR and 13CNMR. Total phenolics and tannins content of the leaves, stems and roots of Plectranthus amboinicus (Lour.) Spreng were determined using Folin-Ciocalteau and Folin-Denis reagents, respectively. Phenolic compounds of the stems and roots were identified using UPLC-MS analysis. Leaves, stems and roots of this plant were tested for antioxidant, anti-inflammatory, analgesic, diuretic, cytotoxic and antimicrobial activities. Results: The isolated compounds were identified as 3-methoxy genkwanin, crisimaritin, p-coumaric acid, caffeic acid, taxifolin, rosmarinic acid, apigenin and 5-O-methyl-luteolin. The stems showed the highest concentration of the total polyphenolics followed by the leaves then the roots (9.6, 8.4 and 5.4 mg/g of gallic acid equivalents, respectively), while the roots recorded the highest tannins content followed by the leaves then the stems (126, 90 and 81 μg/g of tannic acid equivalents, respectively). UPLC-MS analysis revealed the presence of caffeic acid, rosmarinic acid, coumaric acid and chrysoeriol in the stems and roots, while luteolin, quercitin and eriodyctiol were detected only in the stems. The different extracts of the three organs exhibited antioxidant, anti-inflammatory, analgesic, diuretic, cytotoxic and antimicrobial activities with variable potency.