Seedy Banana - A Source of Stilbenes and Flavan-3-ols

Abstract

This study aimed at identifying the bioactive compounds in the seeds of three seedy banana varietiesMusa acuminata, Musa itinerans, and Ensete glaucum. GC-MS of extracts and NMR of isolated compounds were used for the identification of the components and GC-MS/FID was employed for quantification. The proportion of seeds in all samples was around 50% of the dried fruit weight. The seeds were rich in piceatannol, (+)-epiafzelechin, and epiafzelechin dimers. Piceatannol and epiafzelechin dimers were reported in seedy bananas for the first time. The highest piceatannol content was found in Ensete, accounting for 713 ± 71.9 mg/100 g dry weight (DW), followed by the seeds of ripe Musa acuminata and Musa itinerans at 440 ± 56.7 and 242 ± 17.4 mg/100 g DW, respectively. Musa seeds with a higher content of piceatannol had lower concentrations of epiafzelechin and its dimers, in the ranges of 287 to 553 mg/100 g of DW and 533 to 976 mg/100 g of DW, respectively. The content depended on maturity. Compared with ripe fruits, green Musas contained hardly any piceatannol and higher levels of epiafzelechin dimers. Gallocatechin was detected only in Ensete glaucum at 145 ± 19.7 mg/100 g of DW, and a major part of the phenolic compounds in g was found in the seed coat. The identified phenolic compounds in the seeds suggest that seedy bananas could be a potential new crop for food supplements.

Keywords: atropisomerism; bioactive compounds; biorefinery; epiafzelechin; phenolic compounds; piceatannol; seedy banana.

1

Bunches of Musa acuminata (1) and Musa itinerans (2). Fruits of Musa acuminata at green (a) and ripe (b) maturity stages, fruits of Musa itinerans at green (c) and ripe (d) maturity stages, and fruits of green Ensete glaucum (e).

2

Weight fraction of fruit parts of the investigated seedy banana varieties. Mean ± SD (n = 3). Bars carrying different letters for a given part (peel, pulp or seed) are significantly different (p < 0.05).

3

Gas chromatograms of acetone extracts of seeds of ripe fruits (A: Musa acuminata, B: Musa itinerans), and green fruits (C: Ensete glaucum). 1, 2: fructose; 3, 4: glucose; 5: sorbitol/mannitol; 6: palmitic acid; 7: oleic acid; 8: sucrose; 9: (+)-epiafzelechin; 10: piceatannol; 11: epiafzelechin dimers; 12: gallocatechin; ISTD1: margaric acid; ISTD2: resveratrol.

4

Structure of phenolic compounds in seedy bananas confirmed by NMR spectroscopy.

5

Overview of the contents of major bioactive compounds in banana seeds.

6

A) Seeds of Ensete. B) Seeds of Musa. C) Distribution of the phenolic compounds in the seed coats and endosperm of Ensete.