Zipporah M. Onyambu1*, Mildred P. Nawiri1, Hudson N. Nyambaka1 and Naumih M. Noah2
1Department of Chemistry, Kenyatta University, P.O. BOX 43844-00100, Nairobi, Kenya
2School of Pharmacy and Health Sciences, United States International University- Africa (USIU-Africa) P.O BOX 14634-00800 Nairobi, Kenya
Beta carotene (BC), a pro-vitamin A carotenoid found in leafy African indigenous vegetables (LAIVs) and fruits, plays important biological roles towards protection against cardiovascular diseases, cancer and many others. Lack of vitamin A is a major challenge in many developing countries where its source is mainly vegetables. The carotenoid exists as a complex in different food matrices and has to be released from the food matrix for it to be bioaccessible. Different processing procedures affect bioacessibility, boiling and boil-frying being the main thermal processes used by many households in developing countries. The study assessed the bioaccessibility of BC in thermally processed (boiled and boiled-fried) spider plant, cowpeas, amaranth, vine spinach and pumpkin leaves using an in vitro method. After extraction and separation using column chromatography the levels of BC were determined using UV-Vis spectrophotometry. A static gastrointestinal digestion procedure was used to obtain bioaccessible levels of BC. The respective percentage bioaccessibility (%) of BC from spider plant, cowpeas, amaranth, vine spinach and pumpkin leaves were as follows: fresh 97.23±0.01, 81.60±0.36, 77.22±0.05, 61.36±1.87 and 94.48±0.57, boiled 78.80±1.86, 84.31±0.27, 92.28±0.46, 65.67±5.53 and 80.75±0.69, and boiled-fried [48.19±0.82, 31.02±3.09, 16.97±0.02, 23.15±2.82 and 23.33±2.89 respectively. Boiled LAIVs had higher percentage bioaccessibility than boiled-fried due to the effect of longer period of exposure to heat during processing. The knowledge on bioaccessibility of BC from the LAIVs reported in this study would play a key role in encouraging their consumption thus contributing to food security as well as curbing malnutrition.
Keywords: In vitro bioaccessibility; beta carotene; Leafy African Indigenous vegetables; thermal processing