Chemical components of Malakwang (Hibiscus species) leaves and how they are influenced by processing

Abstract

Objectives: This study evaluated the nutritional and phytochemical composition and health claims associated with the red and white Malakwang (Hibiscus species) and how these could be affected by different processing methods. Methodology: The study employed laboratory experimental and longitudinal laboratory experimental. The study was done in Kampala, Gulu, and Kitgum Districts. The results are presented as means with standard error of the mean and tested using Scheffe and Student-Newman-Kuels tests for multiple comparisons. Results: The fresh red Malakwang leaves contained 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 µg) per 100 g when compared to the 1522.2 mg, 1297.9 mg, 179.7 mg, 857.6 µg, and 16.8 µg, for the white respectively. Flavonoids (25.7 %), and alkaloids (5.5%), were higher in the fresh white than the red leaf variety (20.5 % and 2.1 % respectively. The antioxidant percentages of the red (52.7 %) and white (61.3 %) leaf extracts compared favourably with that of ascorbic acid (62.2 %). The biochemical analysis, in Wistar rats fed on the high-fat diet and Malakwang leaf extract, showed a decrease in weight gained up to the fourth week of feeding trial. Acute toxicity calculated based on LD50 values for the white and the red samples were 10,069 and 7224 mg/kg respectively. Cleaning and all cooking procedures led to loss (p<0.05) of crude fat in the white only, B1, B2, B6, B9, and E. by 97-100%.in both red and white. Discarding the cooking liquid lowered (p<0.05) sugar contents to 8.2 and 8.2 mg/100g in the red and white leaf types, respectively. No substantial effect was exhibited in sugar, dietary fibre and protein contents by all drying techniques. All the drying techniques diminished (p<0.05) vitamins C, B1, 2, 6, 9 and tocopherol. Conclusion: Based on the findings, the nutritional composition of the red and white Malakwang leaves were significantly different with respect to crude fat, magnesium, iron, vitamin A (RE) and ascorbic acid. Malakwang leaves can significantly contribute to micronutrient and bioactive components intake in the communities where they are consumed. The phytochemicals compositions were significantly different only in alkaloids and flavonoids. The antioxidant potential of the red and the white leaves were the same and comparable to that of vitamin C. The cooking procedures and the drying techniques were more destructive to vitamin B-complex and E. Cooking for 10 minutes conserved vitamin C better than cooking for 60 minutes. Oven drying at 60ºC retained less moisture. A noticeable potential value of the extracts was demonstrated in regulating low-density lipoprotein cholesterol and urea in the Wistar rats. The two leaf varieties have low toxic levels but the white leaf extract appeared to have a lower toxic level than the red one.