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. 2021 Jul 8;11(1):14116.
doi: 10.1038/s41598-021-93525-w.

Phytochemical composition and antioxidant properties of methanolic extracts of whole and dehulled Bambara groundnut (Vigna subterranea) seeds

Bukola C Adedayo  1 , Tonna A Anyasi  1   2 , Malcolm J C Taylor  3 , Fanie Rautenbauch  4 , Marilize Le Roes-Hill  4 , Victoria A Jideani  5
Affiliations

Phytochemical composition and antioxidant properties of methanolic extracts of whole and dehulled Bambara groundnut (Vigna subterranea) seeds

Bukola C Adedayo et al. Sci Rep. .

Abstract

The distribution of phytochemicals and their contribution to antioxidant potentials in whole and dehulled Bambara groundnut (BGN) seeds was evaluated. Whole BGN seeds were sorted using the testa and hilium colour and further grouped into whole and dehulled BGN seeds. Extractions of both whole and dehulled BGN seeds was done using methanol and the extracts assayed for total phenolics (TPC), flavanol, flavonol, anthocyanin content, oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP). Methanolic extract of whole BGN seed exhibited higher flavanol and flavonol content as well as significantly higher in-vitro antioxidant activities than dehulled BGN seeds. The TPC of whole BGN seed extract ranged from 3.6 to 11.0 GAE/g, while that of dehulled BGN ranged from 2.7 to 3.2 GAE/g. Identification of phenolics in whole and dehulled BGN seed extract using UPLC-qTOF-MS, revealed the presence of monoterpenoids (iridoids), phenolic acids, flavonoids and lignans. Bivariate correlations showed anthocyanin demonstrated weak positive correlation between flavanol, flavonol and ORAC for whole BGN seed extract; and negative correlation between flavanol, TPC, FRAP and ORAC for dehulled BGN. Aside the effect of dehulling, whole BGN seeds exhibited the presence of phytochemicals with beneficial properties for food and industrial application.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Antioxidant properties and total phenolic content of Bambara groundnut seed extracts. (A) Oxygen radical absorbance capacity (ORAC; µmol TE/g); (B) ferric reducing antioxidant property (FRAP; μmol AAE/g); and (C) total polyphenol content (mg GAE/g) of different varieties of whole and dehulled Bambara groundnut. Data represent the mean ± standard deviation of triplicate readings. Different alphabets within each form (whole or dehulled) differ significantly (p < 0.05).
Figure 2
Figure 2
Phytochemicals and mass spectra of identified flavonoids and phenolic acids in Bambara groundnut samples. (A) chromatogram of identified compounds; (B) unfragmented spectra MS1 of compound 4 (m/z 451 and Rt, 9.20); (C) fragmentation spectra MS2 of compound 4 in negative (ESI−) mode; (D) unfragmented MS1 spectra of compound 10 (m/z 691 and Rt, 12.06); (E) fragmentation spectra MS2 of compound 10 in negative (ESI−) mode; (F) unfragmented MS1 spectra of compound 13 (m/z 381 and Rt, 16.32); (G) fragmentation spectra MS2 of compound 13 in negative (ESI−) mode.
Figure 3
Figure 3
Principal component scores and loadings based on Bambara groundnut (A) form, (B) variety with respect to phytochemicals and antioxidant activity.
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