Metabolomics and in-vitro bioactivities studies of fermented Musa paradisiaca pulp: A potential alpha-amylase inhibitor

Abstract

The in-vitro synthesis of bio-compounds via fermentation is a promising route for bioactive molecules intended for disease control and management. Therefore, this study evaluated the effect of fermentation on the antioxidants, antihyperglycemic and anti-inflammatory properties and the resultant chemometric phytochemical profiles of unripe plantain fruits. The results revealed that Escherichia coli and Propionibacterium spp. are suspected as the key fermenters. The E coli showed negative results to the pathogenicity test; Propionibacterium appeared to be opportunistic. A significant increase in the total polyphenols and protein and decreased flavonoids was recorded in the phytochemical profile of the methanolic extract of the fermented unripe plantain pulp; however, the ascorbic acid content was not significantly altered. The ¹H NMR fingerprint showed that there is a closely related chemical shift among the shorter fermentation time (days 2-6) and the unfermented, while the more extended fermentation periods (days 7-12) with enhanced bioactivities were closely related based on the chemometrics analyses. Furthermore, the UPLC-QTOF-MS analysis annotated the presence of bioactive compounds in the day-9 fermented sample: polyhydroxy glucose conjugates (3-Methoxy-4-hydroxyphenyl 6-O-(3,4,5-trihydroxybenzoyl)-beta-D-glucopyranoside), short chain peptide (leucyl-glycyl-glycine), amino acid derivatives (4-Aminophenylalanine, and N-Acetylhistidine), linear and cyclic fatty acid derivatives (palmitoyl putrescine, ricinoleic acid, phytosphingosine, gabalid, rubrenoic acid, 2-aminocyclopentanecarboxylic and cystodienioc acid). The synergistic effect of these newly formed compounds and the increase in the phenolic content of the day-9 fermented unripe plantain may account for its more potent antioxidant, anti-inflammatory and antihyperglycemic activity. Therefore, the products obtained from the day 9 fermentation of unripe plantain pulp may serve as potential nutraceutical agents against gastro-enteric sugar digestion and absorption and sugar-induced oxidative stress, inflammation and metabolic disease.

Keywords: Antioxidants; Diabetes; Fermentation; Inflammation; Metabolomics; Unripe-plantain pulp.

Fig. 1

Effect of Fermentation on the Temperature, pH, phytochemicals and Pearson's correlation coefficients (Heatmap) of percentage change in phytochemical per fermentation intervals of Unripe Plantain Fruits Bacteria and Physicochemical changes: (a) Bacterial growth rate; (b) Changes in temperature and pH of fermented plantain; (c) Total protein content of fermented plantain sample; (d) Ascorbic acid content of fermented plantain sample; (e) Flavonoids content of fermented plantain sample; (f) Total phenolics content of fermented plantain sample. Correlations of fermenters growth with physiochemical changes at a 3-day Interval: (g) Days 1–3, (h) Days 3–5, (i) Days 5–7, (j) Days 7–9, (k) Days 9–11, (l) Days 11–13.

Fig. 2

PCA (a: score plot, b: HCA dendrogram) and OPLS-DA (c: Score plot, d: HCA dendrogram, e: S-plot, f: contribution plot, g: VIP scores) of fermented plantain extracts. The light green spheres and bars represent chemical shifts (ppm) of the region of the S-plot, contributing to the separation of group 1 (light green scores) from group 2 (red scores).

Fig. 3

UPLC-QTOF-MS chromatogram (expanded) of day 2 and 9 samples of the fermented unripe plantain fruits and annotated metabolites: (a) expanded between 0.6 & 4.5 min, (b) expanded between 6.0 & 14.0 min, (c) structures of annotated compounds.