NADES-based extraction of betalains from Terminalia catappa: impact on bioaccessibility, antioxidant capacity, and antimicrobial efficacy.

Terminalia catappa fruit is a neglected red colored plant resource which can be promoted due to its promising organoleptic, nutritional and bioactive compounds. Natural deep eutectic solvents (NADESs) are efficient green solvents used for the extraction of bioactive compounds. In this work, a greener strategy for extracting betalains from T. catappa fruit was implemented using ultrasound-assisted extraction (UAE) combined with four NADESs, including choline chloride: glycerol (CHGLY), choline chloride: ethylene glycol (CHEGLY), choline chloride: lactic acid (CHLA) and choline chloride: acetic acid (CHAC). In addition, the extraction with the conventional solvents, including distilled water, methanol and ethanol, was investigated for comparison. Betacyanin, betaxanthin and total betalain contents were 3.13 ± 0.10-11.53 ± 0.31, 2.82 ± 0.11-9.20 ± 0.22 and 5.95 ± 0.01-20.72 ± 0.53 mg/kg, respectively, with CHLA and CHAC providing the highest contents. The addition of water to CHLA and CHAC significantly affected the recovery of betalains from T. catappa fruit and the highest contents were determined with CHLA+20% distilled water (CHALA2) and CHAC+30% distilled water (CHAC3). The DPPH radical scavenging activity was 220.81 ± 6.44, 350.85 ± 4.39 and 360.23 ± 5.26 mmol TE/g in distilled water, CHAC3 and CHLA2, respectively. ABTS assay resulted in 454.32 ± 4.07, 469.35 ± 3.99 and 461.51 ± 2.28 mmol/g for aqueous, CHAC3 and CHLA2 extracts, respectively. CHLA2 and CHAC3 extracts exhibited the highest in vitro bioaccessibility of betacyanin, betaxanthin, and total betalain throughout the digestive tract compared with the aqueous extract. Moreover, the greatest antimicrobial activity was determined with CHLA2 and CHAC3 compared with the aqueous extract.