[Results and Discussion] The identity of individual phenolic compounds in DBF and DBPS was performed for the first time by HPLC-MS. Detailed HPLC-ESI-QTOF MS analysis showed that in both EPP and HPP fractions, phenolic acids were the most relevant constituents, although some flavanols were also identified in the EPP fraction. Due to the total concentration and profile of individual phenolic compounds in DBF, this product, as an additional source of phenolic compounds in the context of the whole diet, might have health benefits. Indeed, protocatechuic acid was detected in DBF at a concentration higher than that observed in most common foods, according to the Phenol-Explorer database (Neveu et al., 2010). Although the potential effects would be mostly derived from the combination of all phenolic compounds present in this product. Also, regarding the high NEPA content detected in DBF, it should be remarked that other products rich in these phenolic compound fractions, such as grape pomace, have shown several health-related properties, for instance regarding fasting insulin (Martínez-Maqueda et al., 2018). Significant differences between harvest year were detected for some individual phenolic compounds and some phenolic fractions. Nevertheless, for most detected phenolic compounds, identity could not be assigned, since they corresponded to structures not present in common databases or in literature on banana. This indicates the need for further structural analysis in DBF and DBPS to suggest structures for some of these unidentified compounds.

[Introduction] Banana flower (DBF) and banana pseudo-stem (DBPS) are by-products from banana fruit harvest and processing in several industries. The interest in the potential biological activities of these banana residues has been renewed in recent times. Studies on polyphenols have been traditionally focused on the so-called extractable polyphenols (EPP), although increasing evidence is showing the relevance of non-extractable polyphenols (NEPP) or macromolecular antioxidants, which are high molecular weight polyphenols or small ones associated with macromolecules such as protein or dietary fibre (Pérez-Jiménez et al., 2013). Nevertheless, studies on the phytochemical characterization of DBF and DBPS are still scarce and focused on extractable polyphenols (EPP). Thus, Bashkar et al. (2012) is the only found study with these two banana by-products from Musa sp. elakki bale, where HPLC analysis for EPP profile was performed. Also, Schmidt et al. (2015) have reported some characterization of banana male flower and bracts from Musa cavendish in which EPP content by spectrophotometry was measured. Recently, increasing evidence is showing the biological relevance of NEPP (Pérez-Jiménez et al., 2013) and, therefore, there is an interest to identify the presence of these compound on more vegetal materials. The present study aimed to characterize EPP and NEPP profile in DBF and DBPS by HPLC-MS analysis, including the effect of harvest time, to advance towards their use as functional ingredients.

[Materials and Methods] DBPS and DBF were supplied by local producers in 2017 and 2018 for both materials. EPP determination was performed following the protocol by Pérez-Jiménez et al. (2008). NEPP were measured in the residues of EPP extractions as the sum of hydrolysable polyphenols (HPP) and nonextractble proanthocyanidins (NEPA). HPP was determined by the protocol established by Arranz et al. (2009) and Hartzfeld et al. (2002), based on acid hydrolysis with temperature, while determining the butanolysis procedure was applied (Pérez-Jiménez et al. 2009). The EPP and HPP fractions from DBF, as well as HPP fraction of DBPS, were concentrated (6:1) For separation, HPLC with DAD and an ESI-QTOF mass analyzer (Agilent G6530A) was used. Peak identity was established by comparison with the retention times of commercial standards when available and the molecular formula proposed were compared with previously reported phenolic compounds in banana and other vegetal materials.

[Main Conclusion] The detailed analysis of phenolic compounds in DBF (dried banana flower) and DBPS (dried banana pseudo-stem) showed that DBF may be used as an additional source of phenolic compounds, particularly NEPA, although the establishment of accepted content ranges between harvest years may be needed for their use as functional ingredients.

Resumen del póster presentado a la XXX International Conference on Polyphenols, celebrada del 13 al 15 de julio de 2021 en Turku (Finland).

Peer reviewed