Chemical Characterization and Bioaccessibility of Bioactive Compounds from Saponin-Rich Extracts and Their Acid-Hydrolysates Obtained from Fenugreek and Quinoa.

Joaquín Navarro Del Hierro,Diana Martin,Guillermo Reglero

doi:10.3390/foods9091159

Abstract

Saponin-rich extracts from edible seeds have gained increasing interest and their hydrolysis to sapogenin-rich extracts may be an effective strategy to enhance their potential bioactivity. However, it remains necessary to study the resulting chemical modifications of the extracts after hydrolysis as well as their impact on the subsequent bioaccessibility of bioactive compounds. The chemical composition of non-hydrolyzed and hydrolyzed extracts from fenugreek (FE, HFE) and quinoa (QE, HQE), and the bioaccessibility of saponins, sapogenins and other bioactive compounds after an in vitro gastrointestinal digestion was assessed. In general, FE mainly contained saponins (31%), amino acids (6%) and glycerides (5.9%), followed by carbohydrates (3.4%), fatty acids (FFA) (2.3%), phytosterols (0.8%), tocols (0.1%) and phenolics (0.05%). HFE consisted of FFA (35%), sapogenins (8%) and partial glycerides (7%), and were richer in phytosterols (1.9%) and tocols (0.3%). QE mainly contained glycerides (33%), FFA (19%), carbohydrates (16%) and saponins (7.9%), and to a lesser extent alkylresorcinols (1.8%), phytosterols (1.5%), amino acids (1.1%), tocols (0.5%) and phenolics (0.5%). HQE mainly consisted of FFA (57%), partial glycerides (23%) and sapogenins (5.4%), were richer in phytosterols (2.4%), phenolics (1.2%) and tocols (0.7%) but poorer in alkylresorcinols (1%). After in vitro digestion, saponins from FE and QE were fully bioaccessible, sapogenins from HFE displayed a good bioaccessibility (76%) and the sapogenin from HQE was moderately bioaccesible (38%). Digestion of saponin and sapogenin standards suggested that other components of the extracts were enhancing the bioaccessibility. Other minor bioactive compounds (phytosterols, alkylresorcinols, tocols and some phenolics) also displayed optimal bioaccessibility values (70–100%).

Highlights

Fenugreek (Trigonella foenum-graecum L.) and quinoa (Chenopodium quinoa Willd.) are annual crops whose edible seeds have gained special interest in the past decade due to their increasing worldwide production
We recently demonstrated that phytosterols or tocopherols were increased together with sapogenins after the acid hydrolysis of fenugreek and quinoa extracts [22]
The aims of this study were: (1) to tentatively study the modification of the chemical composition of saponin-rich extracts obtained from fenugreek and quinoa seeds after their acid hydrolysis, analyzing changes in the saponin and sapogenin content, as well as the modification in the composition of other co-existing compounds in the extracts; and (2) to assess the bioaccessibility of saponins, sapogenins and other co-existing bioactive compounds of the extracts after the in vitro simulation of the gastrointestinal digestion

Summary

Introduction

Fenugreek (Trigonella foenum-graecum L.) and quinoa (Chenopodium quinoa Willd.) are annual crops whose edible seeds have gained special interest in the past decade due to their increasing worldwide production. Mediterranean region and the Indian subcontinent, the pseudocereal quinoa is an indigenous plant of the Andean region of South America [3,4] Along with their increased production, the gradual introduction of these seeds in Western cuisine has promoted their growing consumption, to the point where these foods nowadays enjoy great consumer acceptance across Europe, North America and other parts of the world [5,6]. Both sweet and bitter varieties, can be eaten boiled in water and as a rice replacement, popped like popcorn, ground to be used as flour and even sprouted [7] Together with their corresponding macronutrients, mainly proteins, carbohydrates and lipids, both seeds are sources of minor bioactive phytochemicals, including saponins, phenolic compounds, phytosterols, carotenoids, alkaloids, tocopherols, and they are rich in essential fatty acids, amino acids, minerals and some vitamins, among many other constituents [8,9]. Current interest in these seeds is focused on their culinary and nutritional properties, and on the obtention of extracts rich in bioactive compounds to be used as nutraceuticals or functional ingredients

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