Investigation of the Phytochemistry and Bioactivity of Two Suregada Species and Morus Mesozygia

Abstract

Microbial infections, inflammation and cancer impose devastating health problems to people globally. The use of drugs is the main mode of management of these ailments. However, emergence of multi-drug resistance strains and undesired side effects has hampered the therapeutic efficacies of many drugs. This has necessitated search for alternative therapeutic agents. The use of plant-based products to manage diseases, including microbial infections, has been in practice long before the development of current medicines and could continue being sources of new drugs in the era of drug resistance. In the present research, the antimicrobial, antiplasmodial, antiviral, antitumor, and anti-inflammatory efficacy of natural-based products from three Kenyan indigenous plants, Suregada zanzibariensis Baill., Suregada procera (Prain) Croizat and Morus mesozygia Stapf. was undertaken. Chromatographic separation of the extracts from these plants gave 32 secondary metabolites of which 2 are new. The configuration of some of the compounds was conducted using ECD and X-ray crystallography. The leaves and roots extract of Suregada procera yielded previously uncharacterized ent-abietaneolide, sureproceriolide A (230) together with seven known secondary metabolites, 8,14β:11,12α-diepoxy-13(15)-abietane-16,12-olide (138), jolkinolide A (140), ent-pimara-8(14),15-dien-19-oic acid (231), 3β-sitosterol (232), oleana-9(11):12-dien-3β-ol (233), jolkinolide E (234), and oleic acid (235). The extract from the roots of S. zanzibariensis yielded six ent-abietane type diterpenoids including; mangiolide (121), jolkinolide B (122), jolkinolide A (140), 7-oxo-ent-abieta-5(6),8(14),13(15)-trien-16,12-olide (131), 7β,11β,12β-trihydroxy-ent–abieta-8(14),13(15)-diene-16,12-olide (236), 8α,14-dihydro-7-oxo-jolkinolide E (237), together with sitosterol (232), scopoletin (238) and vanillin (239). Investigation of Morus mesozygia stem bark extract led to characterization of 16 previously reported metabolites, moracin M (182), moracin N (195), moracin S (216), moracin C (44), artopithecin A (240), mulberrofuran L (241), moracin L (189), moracin D (200), isobavachalcone (243), morachalcone A (209), 2,2՛,4,4՛-tetrahydroxychalcone (208), marsformoxide B (221), betulinic acid (211), 3β-hydroxylup-12-en-28-oic (244), oleanolic acid (245), 4,4′-diphenylmethane-bis(methyl) carbamates (246) and a new 2-arylbenzofuran modified derivative, trivially named mormesozygate (247). The structure elucidation of the isolates was achieved using Nuclear Magnetic Resonance (NMR), Infra-Red (IR), Ultra Violet (UV), Optical Rotation (OR), Mass Spectrometric (MS) techniques as well as by comparison of the NMR data to literature values. In case of compound 140, X-ray crystallography was used...