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

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%).

Functional Components and Anti-Nutritional Factors in Gluten-Free Grains: A Focus on Quinoa Seeds

“…γ-Tocopherol was also the most abundant in the commercial quinoa samples studied by Niro et al (Table 5) [58]. On the other hand, β-tocopherol was found in samples of commercial red quinoa (Table 5) [50].The bioaccessibility of βtocopherol was also detected in the hydrolyzed extracts of quinoa and proved to be high (≈70%).…”

“…Serjanic acid, oleanolic acid, phytolaccagenic acid and hederagenin were the four aglycones identified in commercial quinoa samples [50,72]. The highest total saponin (TS) was found in red quinoa extracts by Navarro del Hierro et al and decreased to 20 g kg −1 upon extraction after hydrolysis of the sample (Table 6) [50]. No sapogenins were detected in the non-hydrolyzed quinoa extract, while the sapogenin content was 56.3 g kg −1 in the hydrolyzed extract (Table 6).…”

“…In ethanolic extracts of quinoa seeds purchased in local markets in Central Italy, 4 -geranyloxyferulic acid was found [49]. In both methanolic and hydrolyzed extracts of commercial red quinoa, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, protocatechuic acid, isoferulic acid, vanillic acid, and the flavonoid quercetin were identified by GC-MS, (Table 3) [50]. Vanillic was the most abundant phenolic acid in quinoa samples purchased in Seoul (Korea), while gallic and chlorogenic acids occurred in traces (Table 3) [45].…”

Saponin-Rich Extracts and Their Acid Hydrolysates Differentially Target Colorectal Cancer Metabolism in the Frame of Precision Nutrition

“…Due to the potential of these molecules as bioactive agents, great efforts are being made to obtain saponin and sapogenin-rich extracts using non-conventional extraction methods, such as ultrasound-assisted extraction (UAE), which reduces time and energy consumption and augments the extraction efficiency. In a recent work, we produced UAE extracts from fenugreek and quinoa in order to obtain saponin-rich extracts from these popular edible seeds rich in both types of sapogenins, namely steroid and triterpenoid saponins (FE and QE), respectively [ 22 ]. Subsequently, the acid hydrolysis of these extracts was performed in order to obtain sapogenin-rich extracts (HFE and HQE), which was proposed as an innovative technological strategy to produce novel natural extracts with potential improved bioactivity.…”

“…Subsequently, the acid hydrolysis of these extracts was performed in order to obtain sapogenin-rich extracts (HFE and HQE), which was proposed as an innovative technological strategy to produce novel natural extracts with potential improved bioactivity. This is because, interestingly, in addition to sapogenins, different bioactive compounds of potential interest such as phytosterols, phenolic compounds, alkylresorcinols, tocopherol, or lipids were also identified in such extracts [ 22 ].…”