In vitro Bioaccessibility of Beta Carotene from Thermally Processed Leafy African Indigenous Vegetables

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.


In vitro bioaccessibility; beta carotene; Leafy African Indigenous vegetables; thermal processing

Onyambu et al. JKCS 14-1 (2021) 3-8

Trace Elements in Carbonated Cold Springs of Eastern Mt. Kenya, Meru County

George N. Mungai1, 2*, Hellen N. Njenga1, Eliud M. Mathu3 and Vincent O. Madadi1
1Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
2Department of Physical Sciences, Meru University of Science and Technology, P.O. Box 972 60200, Meru, Kenya
3Department of Geology and Meteorology, South Eastern Kenya University, P.O. Box 170-90200, Kitui, Kenya

Carbonated spring waters are natural sources of trace minerals considered to have important biological and therapeutic functions. However, some trace elements are toxic to the human body upon exposure even at low concentration levels. Ten carbonated springs located in Meru County, on the Eastern Slopes of Mt. Kenya were investigated to determine the levels of trace elements. The host communities draw the carbonated mineral waters regularly for drinking, cooking, watering the livestock and selling. Cavity ring-down spectroscopy was used for the analysis of dissolved inorganic carbon in the spring waters and inductively coupled plasma-optical emission spectrometry for the determination of the following trace elements: As, B, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se and Zn. Host rocks analysis for major toxic elements As, Cd, Cr, Cu, Hg and Pb was done by X-ray fluorescence. The reported dissolved inorganic carbon in the waters was significant ranging from 39.2-89.0 mmol/kg and this enhanced dissolution of minerals from rocks due to the presence of carbonic acid. Levels of As in six springs ranged from 11.1 to 21.5 μg/L and exceeded the 10 μg/L WHO recommended limit for drinking-water. There was a strong positive correlation with r = +0.8, between As levels and dissolved inorganic carbon. The other elements were within the safe limit. Toxic elements in the rocks ranged from As 30-170 ppm, Cd <10 ppm, Cr <10-100 ppm, Cu 40-180 ppm, Hg <10 ppm and Pb <10-370 ppm. Therefore, water-rock interaction contributed significantly to the presence of toxic elements in the carbonated waters. Arsenic (As) is a well-known carcinogen and poses many other health risks to humans. An epidemiological study on clinical manifestations of As toxicity in the region as well as removal of As from the waters prior to consumption are recommended.


Arsenic toxicity, carbonated springs, mineral waters, trace minerals

Mungai et al. JKCS 14-1 (2021), 9-16