Phytochemical composition of four selected vegetable spices commonly consumed in Malawi

Abstract

Spices, regardless of source, play an important role in enhancing or improving flavor of foods or dishes. In this study, determination of phytochemical composition with respect to total phenolic compounds, antioxidant capacity and vitamin C was conducted in four selected vegetable spices consumed in Malawi, namely Allium cepa L, Allium sativum L, green bell pepper (Capsicum annum L.) and Zingiber officinale. Results showed that total phenolic composition, in mg GAE/100 g, was highest in Zingiber officinale rhizomes (326.5±0.39) followed by Allium cepa L. (169.7±0.00), green bell pepper (124.9±0.20) and Allium sativum L. (72.72±0.39), respectively. Results further showed that Zingiber officinale had the highest antioxidant capacity and reducing power and the lowest vitamin C content, in the range of 21.78±0.21 mg AAE/100 g, 24.35±2.24 mg AAE/g and 3.61±0.23 mg AAE/100 g, respectively compared to the other vegetable spices. On the other hand, vitamin C content was highest in Allium sativum L followed by red Allium cepa L registering values of 455.0±2.12 and 443.4±2.50 mg AAE/100 g, respectively. The reducing power (in mg AAE/g) of the vegetable spices was highest in green bell pepper (Capsicum annum L.) with the value of 17.11±1.549 followed by red Allium cepa L. (9.519±0.860) and Allium sativum L. (5.922±0.778), respectively. Total tannins content, in mg TAE/g, was highest in Allium sativum L, which registered the value of 159.56±4.84 followed by Zingiber officinale (91.53±0.33), bell  pepper (79.94±0.21) and Allium cepa L (49.36±1.98). Furthermore, phytic acid and oxalic acid contents were highest in Zingiber officinale registering values of 5.504±0.822 mg/kg and 37.25±2.83 mg/g, respectively. Red Allium cepa L. was found to contain 20.53±0.916 mg/g oxalic acid but had the lowest phytic acid content registering the value of 2.057±0.095 mg/kg. It can be concluded that the high phytochemical composition in the four vegetable spices, with low antinutrients like phytic and oxalic acids, can play an important role in improving human nutrition and health of consumers.