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The present study describes the effects of germination on nonnutritional factors and antioxidant activity in the nonconventional legumes Vigna unguiculata (cowpea), Canavalia ensiformis (jack bean), Lablab purpureus (dolichos), and Stizolobium niveum (mucuna). Protease inhibitors and lectins were detected in raw legumes and were significantly decreased during the germination. Regarding total and individual inositol phosphates (IP5-IP3), important reductions of IP6 and high increases in the rest of inositol phosphates were also detected during this process. In addition, total phenols, catechins, and proanthocyanidins increased, accompanied by an overall rise of antioxidant activity (79.6 μmol of Trolox/g of DW in the case of mucuna). Germination has been shown to be a very effective process to reduce nonnutritional factors and increase bioactive phenolic compounds and antioxidant activities of these nonconventional legumes. For this reason, they could be used as ingredients to obtain high-value legume flours for food formulation.

BACKGROUND Typical hydrolysis times of saponins generally do not take into consideration the effect of time on the degradation of the target compounds, namely sapogenins. When producing natural extracts, it should be borne in mind that conducting hydrolysis to yield a target compound might also affect the final composition of the extracts in terms of other bioactive compounds. In our study, saponin‐rich extracts from fenugreek, quinoa, lentil, and soybean were produced and their acid hydrolysis to give sapogenin‐rich extracts was conducted over different periods (0–6 h). The disappearance of saponins and appearance of sapogenins was analyzed using high‐performance liquid chromatography–diode array detection–mass spectrometry (HPLC‐DAD‐MS) and gas chromatography–mass spectrometry (GC‐MS), respectively. The impact of hydrolysis on the phytosterols and tocopherol in the extracts was also evaluated. RESULTS Fenugreek showed the highest saponin content (169 g kg−1), followed by lentil (20 g kg−1), quinoa (15 g kg−1), and soybean (13 g kg−1). Hydrolysis for 1 h caused the complete disappearance of saponins and the greatest release of sapogenins. Hydrolyzed fenugreek and quinoa extracts contained the highest amounts of sapogenins and minor fractions of phytosterols and tocopherol. Hydrolyzed extracts of lentil and soybean contained a major fraction of phytosterols and a low fraction of sapogenins. In all cases, sapogenins decreased after 1 h of hydrolysis, phytosterols slightly decreased, and tocopherol was unaffected. Standards of diosgenin and oleanolic acid also showed this decreasing pattern under acid hydrolysis conditions. CONCLUSION Hydrolysis times of 1 h for saponin‐rich extracts from the assayed seeds guarantee the maximum transformation to sapogenin‐rich extracts, along with phytosterols and tocopherol. Fenugreek and quinoa seeds are preferred for this. © 2018 Society of Chemical Industry