Nutritional, phytochemical composition and antioxidant activities of the red and white malakwang (hibiscus species) leaves

Abstract

Malakwang (Hibiscus species) is a common vegetable in Uganda diets. This study established the nutritional, phytochemical composition, and antioxidant activities of the red and white malakwang leaves. Malakwang leaves were harvested six weeks after germination. Nutrients and phytochemicals were quantified and qualified using the methods of Association of Official Analytical Chemists (AOAC) and HighPerformance Liquid Chromatography (HPLC). The antioxidant activity was determined using the 2, 2- Diphenyl-1-picrylhydrazyl (DPPH) scavenging method. The quantity of crude fat was significantly higher (p<0.05) in the white malakwang leaf samples (6.9 %) than the red (3.3%). The red had significantly higher (p<0.05) quantities of calcium (1753.6 mg), magnesium (1814.4 mg), iron (233.4 mg), vitamin A (RE) (952.7 µg) and vitamin E (22.8) per 100 g when compared to the 1522.2 mg, 1297.9 mg, 179.7 mg, 857.6 µg, and 16.8 µg, respectively for the white malakwang leaves. The white malakwang leaf samples had higher (p<0.05) quantities of flavonoids (25.7 %) and alkaloids (5.5) than the 20.7 % and 2.1 %, respectively for the red malakwang leaves. The red malakwang leaf extract had more mucilage and coumarin contents than the white malakwang leaves. The white and red leaf extracts scavenged 61.3% and 52.7% of DPPH radicals, respectively, which are similar to the 62.2% scavenged by vitamin C. Malakwang leaves could significantly contribute to dietary intake of crude fibre, essential oil, calcium, magnesium, zinc, vitamin A (RE), C and E and phytochemicals hence suggesting a correlation with the cultural health claims for improving breast milk production, appetite, immunity and healing of sores and wounds. Further studies on the evaluation of nutrients and phytochemicals in malakwang leaves are recommended to approve the results of this study. Experimental trials in humans could be performed to evidence the effect of malakwang leaves on breast milk production and healing of sores and wounds. Also, the determination of essential fatty acids and the effect of preparation and postharvest methods are recommended for further studies.