High valuable compounds from the unripe peel of several Musa species cultivated in Madeira Island (Portugal)

Abstract

The lipophilic extractives of the unripe peel of ten banana cultivars belonging to the Musa acuminata and Musa balbisiana species (namely ‘Giant Cavendish’, ‘Chinese Cavendish’, ‘Grand Nain’, ‘Gruesa’, ‘Williams’, ‘Ricasa’, ‘Eilon’, ‘Zelig’, ‘Dwarf Red’ and ‘Silver’) were studied by gas chromatography–mass spectrometry. The extractives content were in the range of 2–3% with substantially higher values for ‘Silver’ and ‘Dwarf Red’ (5.7 and 10.7% respectively). Sterols and fatty acids were the major families of compounds identified, with respectively 55.1–87.5% and 10.6–43.2% of total of lipophilic components. Cycloeucalenone was the main component identified in ‘Williams’ and ‘Dwarf Red’, with abundances ranging from 806 to 9453 mg Kg⁻¹ of dry unripe peels, respectively. The identification of high contents of valuable compounds, can open new strategies for the valorization of the studied banana residues and particularly of those from ‘Dwarf Red’ followed by ‘Silver’ and ‘Ricasa’, as potential sources of high-value phytochemicals.

Introduction

Banana and plantain (Musa spp.) are major tropical and sub-tropical sources of food and raw materials. Bananas are cultivated in over 130 countries and grow over a harvested area of approximately 10 million hectares. The annual world production accounts for about 80 million tons, with India as the major producer with about 26 million tons (FAO, 2009).

The genus Musa is composed of four sections: Australimusa, Callimusa, Musa and Rhodochlam. Most edible bananas are originated from two species of the section Musa: M. acuminata and M. balbisiana. The cultivars are either hybrids among subspecies of M. acuminata (ploid type A) or between M. acuminata and M. balbisiana (ploid type B). The most important banana cultivars are triploid AAA and plantains are mostly AAB, ABB or BBB (Ball et al., 2006). Due to the difficulty of breeding infertile plants, only a few cultivars have been introduced in the last 50 years. The advent of clonal propagation, combined with selection programs, led to the singling out of “elite” clones in terms of yield and fruit quality, adapted to the agro-ecological conditions.

Banana crop was introduced in Madeira Island in the sixteenth century and nowadays banana plantations occupy about 11% of agricultural area and represent 20% of the agricultural production and 1/3 of the exports of the Island. Finally, this plantation is currently considered as essential to protect the natural landscape of the region (Ribeiro and Silva, 1998).

The cultivar ‘Dwarf Cavendish’ is the most important, comprising ca. 60% of the total banana production in Madeira. However, recent changes in European Union Policies prompt farmers to select and grow other varieties (Council Regulation, 2006). As a response, new banana cultivars have been introduced in the region and some of them have already been released to farmers (Ribeiro and Silva, 1998).

After harvesting of the single bunch of bananas, a huge amount of residues are produced (banana plant and unripe banana residues). The banana plant residues (pseudostem, foliage, and rachis) are usually left in the soil plantation and used as fertilizer. The unripe banana residues are produced mainly during their selection process in the collection stations where the bananas too small for shipping or those with damaged or spoiled areas, are removed. These rejected bananas are normally improperly disposed, causing environmental problems. Different strategies have been suggested for the valorization of these wastes such as in flours, dried pulps, jams in animal feed or eventually composted (Zhang et al., 2005); for the production of biofuels (Bardiya and Somayaji, 1996, Hammond et al., 1996, Tewari et al., 1986), or as adsorbents for water purification (Annadurai et al., 2002, Annadurai et al., 2003). Finally, banana peel extracts were also used for phytopharmaceutical applications (Gene, 1999).

In a previous study, we reported a detailed study on the lipophilic extracts from unripe pulp and peel of banana fruit of ‘Dwarf Cavendish’ (Oliveira et al., 2008), where high amounts of fatty acids and particularly, free sterols, steryl esters, and steryl glucosides were found.

The importance of banana crops in Madeira Island and the detection of valuable compounds in ‘Dwarf Cavendish’ extracts (Oliveira et al., 2008), lead us to study new varieties introduced in Madeira Island in order to access their potential as sources of high value phytochemicals with nutraceutical applications. Banana peels lipophilic extracts from ten subspecies of M. acuminata (AAA) and hybrids from M. acuminata and M. balbisiana (AAB and ABB), namely ‘Giant Cavendish’, ‘Chinese Cavendish’, ‘Grand Nain’, ‘Gruesa’, ‘Williams’, ‘Ricasa’, Eilon’, ‘Zelig’, ‘Dwarf Red’ and ‘Silver’ were surveyed in the present study by gas chromatography–mass spectrometry (GC–MS) analysis.