Oral Presentation 49th Nutrition Society of Australia Annual Scientific Meeting 2025

Antioxidant capacity and phytochemical bioaccessibility of finger lime (Citrus australasica) extracts during in vitro digestion (129903)

Nguyen-Phuc Le 1 , Alice Lee 1 , Jayashree Arcot 1
  1. Food and Health group, School of Chemical Engineering, UNSW Sydney, Sydney, NSW 2032, New South Wales, Australia

In this study, ultrasound-assisted extraction (UAE) was applied to finger lime (Citrus australasica), a native Australian citrus rich in ascorbic acid and polyphenols(1), to optimize antioxidant yield and evaluate bioaccessibility. Dried peel, flesh, and peel–flesh freeze-dried powders were extracted at amplitudes of 10%, 30%, and 50% for 10, 15, or 20 minutes, and total phenolic content (TPC), DPPH radical-scavenging activity, and ferric reducing antioxidant power (FRAP) were measured (means ± SD; p < 0.05). The optimal UAE condition was 30% amplitude for 20 minutes, under which peel extracts showed the highest values (TPC: 12.33 ± 0.59 mg GAE/g DW; DPPH: 3.64 ± 0.15 mg TE/g DW; FRAP: 5.96 ± 0.33 mg TE/g DW), significantly higher than those of other conditions. These optimized extracts were subjected to the standardized INFOGEST 2.0 static in vitro digestion (oral, gastric, intestinal) to assess antioxidant stability and phytochemical bioaccessibility(2). The antioxidant capacity decreased gradually during digestion, with the largest reductions occurring during the intestinal phase. Specifically, the FRAP value of the peel extracts declined from 6.06 ± 0.34 to 3.03 ± 0.18 mg TE/g DW, with similar patterns observed for TPC and DPPH. Targeted HPLC–PDA analysis showed significant intestinal losses of vitamin C content in the extracts (peel: 170.48 ± 7.33 to 11.37 ± 0.83 mg/100 g DW – 93.33% loss; peel–flesh mixture: 429.98 ± 2.34 to 24.30 ± 1.67 mg/100 g DW – 94.35% loss). In contrast, the main citrus flavanones, naringin and naringenin, were more stable across phases, compared to ascorbic acid under simulated gastrointestinal conditions. These findings illustrate the changes in finger lime bioactive content under gastrointestinal conditions and highlight the importance of considering compound stability in the development of functional foods from Australian native resources.

Keywords: finger lime; ultrasound-assisted extraction; bioaccessibility; antioxidant.

Ethics Declaration

N/A

Financial Support

N-P Le was supported for his PhD studies through the University International Postgraduate Award (UIPA) from UNSW Sydney.

References

  1. Qi Y, Liu H, Agar OT et al. (2024) Food Rev Int 40, 2167–2187.
  2. Brodkorb A, Egger L, Alminger M et al. (2019) Nat Protoc 14, 991–1014.