Evaluation of antioxidant, anti-inflammatory and anti-diabetic properties of noni fruit (Morinda citrifolia L.) and its simulated gastrointestinal digesta fractions

Noni (Morinda citrifolia L.) has been used for years in traditional medicine. As noni fruit is not utilized by the food industry in Sri Lanka, this study focused on determining the bioactives and functional properties of ripe fruit extract (methanolic and water) and simulated gastrointestinal digesta fractions. Methanol (80%) showed higher extractability of bioactives than water. Moreover, antioxidant and anti-inflammatory properties were higher, and anti-diabetic properties were lower in methanolic extracts than those in water extracts. The total phenolics (TPC) of 198.6 ± 2.48 μmol gallic acid equivalent/g FW, and ascorbic acid, anthocyanin, and β-carotene contents of 53.01 ± 1.47, 57.33 ± 1.01, and 0.27 ± 0.04 μg/g FW, respectively were evident in the fresh fruit. DPPH and ABTS radicals scavenging percentages of the fresh fruit were 97.09 and 98.98, respectively. The total antioxidant capacity of the fresh fruit was 33.94 mg AAE/g FW. Singlet oxygen and Nitric oxide scavenging abilities of the fresh fruit were above 90%. Percentages of heat-induced hemolysis, protein denaturation inhibition, and proteinase inhibitory activities of the fresh fruit at 2 µg/mL were 37.14, 42.32, and 5.23, respectively. Furthermore, alpha-amylase and alpha-glucosidase inhibitory activities of the fresh fruit at 2 µg/mL were 13.7 and 17.0%, respectively. Bioactives and antioxidant, anti-diabetic, and anti-inflammatory activities of dialysable fractions were significantly lower (p < 0.05) than their originals. Positive correlations between TPC and antioxidant activities, and anti-inflammatory and antioxidant activities were evident. This study revealed the therapeutic benefits and appealing sensory attributes that should be developed when producing Noni fruit-incorporated products.