Profile of phenolic compounds and antioxidant activity of finger millet varieties.

The profiles of phenolic compounds and antioxidant capacities of four finger millet varieties harvested in northern Malawi were investigated. The total phenolics, flavonoids and condensed tannins in the free fractions ranged from 114.43 to 179.19 mg ferulic acid equivalent (FAE)/100 g, 90.24 to 202.94 mg catechin equivalent (CE)/100 g and 31.76 to 83.59 mg CE/100 g, respectively. Total phenolic contents of the bound fractions ranged from 58.27 to 123.23 mg FAE/100 g. Twenty phenolic compounds were identified in the free fractions including eighteen flavonoids, with catechin and epicatechin being the predominant flavonoids. Seventeen phenolic compounds were identified in the bound fractions, with ferulic acid being the predominant one. Ten of the identified polyphenols were firstly reported in finger millet. Darker colored finger millet varieties had higher phenolic contents and antioxidant properties than the lighter colored ones. Finger millet can be used as healthy food material and natural antioxidant resource.

Comparison of Phytochemicals and Antioxidant Capacity in Three Bean Varieties Grown in Central Malawi.

The aims of the current work were: (1) to study the influence of variety and geographical production area on the total phenolic content, total anthocyanin content, total flavonoid content, total carotenoid content and antioxidant activity in bean varieties (Dimeta, Napirira and Nanyati) from different growing areas in central Malawi, and (2) to evaluate the possibility of establishing a classification based on the geographical areas of the growing regions. A total of 47 bean samples were collected from Makowe, Mphathi, Chuma-Chitsala and Khulungira Zone. These four locations were segregated based on altitude, latitude and longitude. Principal component and hierarchical cluster analysis were used to distinguish and classify among these samples. Significant differences (P < 0.05) in total phenolic content (2.92-4.97 mg/g), total anthocyanin content (14.52-152.31 µg/g), total flavonoid content (2.01-6.38 mg/g) and oxygen radical absorbance capacity (16.75-24.51 µmol/g) were found among the different sampled villages, showing a significant effect of the producing region on these parameters. The beans in Makowe had lower polyphenols than in other locations. Results of principal component analysis indicate that phytochemicals and antioxidant capacity could serve as parameters to establish a bean classification according to the geographical area of production.

Provitamin A potential of landrace orange maize variety (Zea mays L.) grown in different geographical locations of central Malawi.

The provitamin A potential of landrace orange maize from different locations (A, B, C and D) of central Malawi has been evaluated. Physicochemical compositions, color, total carotenoid content (TCC), carotenoid profiles, and oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging activity as antioxidant capacities of maize were determined. Color values of orange maize had correlations with ß-cryptoxanthin (r>0.36). TCC of white and orange maize averaged 2.12 and 59.5 mg/kg, respectively. Lutein was the most abundant carotenoid (47.8%) in orange maize, followed by zeaxanthin (24.2%), ß-carotene (16.4%) and ß-cryptoxanthin (11.6%). Location D showed the highest levels of lutein, zeaxanthin and antioxidant capacity. Provitamin A content of orange maize met the target level (15 µg/g) of biofortification. Retinol activity equivalent (RAE) from ß-cryptoxanthin and ß-carotene in orange maize averaged 81.73 µg/100g. In conclusion, orange maize has the potential to be a natural source of provitamin A.

Distribution of carotenoids in endosperm, germ, and aleurone fractions of cereal grain kernels.

To compare the distribution of carotenoids across the grain, non-corn and corn cereals were hand dissected into endosperm, germ and aleurone fractions. Total carotenoid content (TCC) and carotenoid composition were analysed using spectrophotometry and HPLC. Cereal carotenoid composition was similar; however, concentrations varied significantly (p<0.05). Endosperm fractions had TCC ranging from 0.88 to 2.27 and 14.17 to 31.35 mg/kg in non-corn cereals and corn, respectively. TCC, lutein and zeaxanthin in germ fractions were higher in non-corn cereals than in corn. Lutein and zeaxanthin contents were lower in non-corn cereal endosperms. The aleurone layer had zeaxanthin levels 2- to 5-fold higher than lutein among the cereals. Positive significant correlations (p<0.05) were found between TCC, carotenoids analysed by HPLC and DPPH results. This study is the first to report on carotenoid composition of the aleurone layer. Our findings suggest that the aleurone of wheat, oat, corn and germ of barley have significantly enhanced carotenoid levels.