Bioactive constituents from Manilkara obovata (Sabine & G.Don) J.H.Hemsl

Abstract

The phytochemical investigation of the methanolic extracts of roots, stem bark, leaves and twigs of Manilkara obovata has led to the isolation of one new friedelane triterpene, lacefriedelic acid or 3β,23-dihydroxy D:A-friedooleanan-28-oic acid (1) and one new prenylated xanthone, lacexanthone or 4,7-dihydroxy-2,3,3,9,9-pentamethyl-2,2-dihydrofurano[2,3-a]pyrano[2,3-i]xanthen-13(9H)-one (2) alongside twenty-four known compounds. Compounds 1-11 are reported here for the first time from the genus Manilkara. The structures of all compounds were determined by spectroscopic analyses and X-ray crystallography. The methanolic extracts of twigs and leaves showed anti-oxidant activity of 93.2 and 91.1%, respectively, at 100 µg/mL when measured by DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), while the twig extract displayed 86.3% at 100 µg/mL against the urease inhibition assay. Some isolated compounds (1-4, 15 and 20) showed significant to moderate anti-oxidant activity and urease inhibition assay. It is estimated that significantly active anti-oxidants and urease inhibitors metabolized by the plant may find future application in food industry.

Graphical Abstract

Keywords:

• Manilkara obovata
• friedelane triterpenoid
• lacexanthone
• xanthones
• anti-oxidant activity
• urease inhibition
• chymotrypsin inhibition

Acknowledgements

The authors are grateful to the International Centre for Chemical and Biological Sciences (ICCBS), University of Karachi-Pakistan for research facilities and the World Academy of Sciences (TWAS), Italy for supporting an ICCBS-TWAS sandwich program, to the YABINAPA Graduate School for providing research facilities in Cameroon. The authors also wish to thank the Alexander von Humboldt Foundation, Germany for Research Group Linkage funding 2015-2018 of the Norbert Sewald/Jean Duplex Wansi research group cooperation, for the return fellowship 2019 (JDW) and for generous support with laboratory equipment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funded by Alexander von Humboldt-Stiftung; Deutscher Akademischer Austauschdienst; The Academy of Sciences for the Developing World.