New bioactive flavonoid glycosides with antioxidant activity from the stem bark of Olax subscorpioidea Oliv

Bienvenu Tsakem, Roland Tchuenteu Tchuenguem, Xavier Siwe-Noundou, Beaudelaire Ponou Kemvoufo, Jean Paul Dzoyem, Rémy Bertrand Teponno*, Rui Werner Macedo Krause, Léon Azefack Tapondjou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A previously unreported gallocatechin glycoside, (2 R,3S) 4′-O-methyl-gallocatechin-3-O-α-ʟ-rhamnopyranoside (1) and an unseparable mixture of two previously undescribed dihydromyricetin glycosides, (2 R,3R) 4′-O-methyl-dihydromyricetin-3-O-α-ʟ-rhamnopyranoside (2a) and (2 R,3S) 4′-O-methyl-dihydromyricetin-3-O-α-ʟ-rhamnopyranoside (2 b) along with three known compounds were isolated from the n-butanol soluble fraction of the stem bark of Olax subscorpioidea Oliv. Their structures were elucidated by detailed spectroscopic analyses, including 1H NMR, 13C NMR, 1H-1H COSY, HSQC, HMBC, NOESY, HR-ESI-MS and chemical methods. The crude ethanol extract, the fractions, and some of the isolated compounds were screened for their antioxidant and antibacterial activities. They showed significant antioxidant activities with EC50 ranging from 6.29 to 18.19 µg/mL in 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and EC50 ranging from 85.77 to 86.39 mmol FeSO4/g in ferric reducing antioxidant power (FRAP) methods compared with 2.29 µg/mL and 3.52 mmol FeSO4/g for the positive control (ʟ-ascorbic acid). Nevertheless, no inhibition was observed against the tested bacterial strains at a MIC less than 256 μg/mL.

Original languageEnglish
JournalNatural Product Research
DOIs
Publication statusAccepted/In press - 2022
Externally publishedYes

Keywords

  • antioxidant activity
  • dihydromyricetin
  • flavonoid glycosides
  • gallocatechin
  • Olax subscorpioidea
  • structural elucidation

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