Abstract
Background: Plectranthus cylindraceus, a bushy leafy herb, is commonly used in folk medicine in some countries such as Saudi Arabia for the treatment of sore throats, skin, digestive and respiratory diseases and for personal hygiene as deodorant and disinfectant. Its oil is reported to possess antimicrobial, nematicidal, and antioxidant activities. Previous phytochemical investigation of P. cylindraceus resulted in the isolation of sesquiterpenes and flavonoids as main constituents of the plant. The aim of present study is to isolate and identify new chemical constituents from the Saudi Arabian P. cylindraceus.
Method: The crude MeOH extract was separated by vacuum liquid chromatography (VLC), using hexane, EtOAc, and MeOH. The EtOAc fraction was chromatographed on silica gel, sephadex LH-20, and RP18 columns, affording four compounds. The structure elucidation of these compounds was achieved with the aid of 1D and 2D NMR (1H-1H COSY, HSQC, and HMBC) as well as HR-MS and comparison with literature. Results: Four pure compounds were isolated and identified as: maaliol (1), plectranol A (2), penduletin (3), and chrysosplenol D (4) from MeOH extract of P. cylindraceus. Conclusion: A new sesquiterpene, namely plectranol A (2), along with three known compounds, was isolated from the aerial parts of Plectranthus cylindraceus.Keywords: Flavonoids, Lamiaceae, plectranol A, Plectranthus cylindraceus, sesquiterpene, VLC.
Graphical Abstract
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