Evaluation of nutrient composition and antioxidant properties of selected commonly consumed and underutilised seasonal fruits in nsukka metropolis

Thesis Abstract

The increased interest in antioxidant activity of plant phytochemicals has necessitated their determination in rarely consumed fruits. The aim of this study was to determine the antioxidant capacity as well as the vitamin and mineral content of the selected commonly consumed and underutilized fruits. Samples of six selected commonly consumed fruits; pineapple (Ananas comosus) and banana (Musa acuminata) and underutilized fruits; soursop (Annona muricata), African canarium (Canarium schweinfurthii), african star apple (Chrysophyllum albidum) and tangerine (Citrus tangerina) were collected from the local market and analysed for antioxidant capacity using the free radical scavenging activity. The stable radical 1,1-diphenyl-2-picrylhydrazil (DPPH) and ferrous reducing antioxidant power (FRAP) assay were used.Antioxidant vitamins A,C,E and trace minerals were determined. The proximate analysis of the fruit pulps showed that C. albidum and C. schweinfurthii had the highest percentage of carbohydrate (22.41± 0.00 % and 21.37 ± 0.00 % respectively) while C. tangerina had the least (2.34 ± 0.00 %). C. schweinfurthii had the highest percentage of fat (19.41 ± 0.00 %) relative to the other fruit pulps. Tannins level was significantly (p<0.05) higher in M. acuminata(7.99 ± 0.00 mg/100g), terpenoids and saponin levels were also significantly (p<0.05) higher in C. schweinfurthii (56.92 ± 0.15 mg/100g and 1.03 ± 0.02 mg/100g respectively) when compared to control and other underutilized fruit pulps. For flavonoid content, C. schweinfurthii and A. muricata had the highest values (32.27 r± 0.16 mg/100g and 30.13 ± 0.04 mg/100g respectively) while A. comosus had the least (7.20 ± 0.03 mg/100g). Vitamin C level was significantly (p<0.05) higher in C. schweinfurthii and C. albidum (484.80 ± 2.1 mg/100g and 479.41 ± 0.7 mg/100g) respectively compared to the control. C. tangerina had the highest vitamin A levels (206.89 ± 4.9 mg/100g) while M. acuminata and A. comosus showed the highest level of vitamin E (74.48 ± 0.0 mg/100g and 59.42 ± 0.0 mg/100g) respectively. Selenium, zinc, potassium, calcium and iron levels were significantly (p<0.05) higher in C. albidum and C. schweinfurthii relative to the other fruit pulps studied. C. albidum had the highest level of % inhibition (73.07%) relative to other fruit pulps while M. acuminata had the least % inhibition (31.12%). Ferric reducing power activity of the fruit pulps revealed significant increase in A. comosus and M. acuminata with increasing concentrations. M. acuminata had the highest reducing power activity (0.655 mg/ml) at the highest concentration (1mg/ml) while A. muricata had the least at (0.01mg/ml). In conclusion, among selected fruits, underutilized fruits have shown relatively higher level of antioxidant capacityand contain appreciable amount of essential nutrients, vitamins and minerals than the commonly consumed fruits. Especially African star apple and African canarium are good sources of antioxidants. The study further showed that no single plant food could provide all the required nutrients.