Roselle (Hibiscus sabdariffa L.) seeds - nutritional composition, protein quality and health benefits.

Roselle (Hibiscus sabdariffa Linn) is a herbal shrub plant reported native to tropical Africa and grown in warm countries including Malaysia. This plant is grown for the calyces or petals of the flower which are mainly used to prepare herbal drink, beverages, jam and jellies. After removing the calyces, the velvety capsules containing the seeds are disposed as a by-product. In addition, it is a waste if the seeds are left untouched, without effort to exploit its usefulness and benefits. Moreover, with limited research on the usefulness of roselle seeds, no review paper on this topic has ever published. Thus, we took the initiative to prepare a review on this subject based on findings from most of our work from 2003-2007. In this paper, the most important aspects namely, nutritional composition, including antioxidant properties, protein quality and the effect of seeds on lipid profiles of hypercholesterolemic rats have been reviewed. Based on the compositional analysis, roselle seeds are rich in nutritional components especially proteins, oil and dietary fiber. The seeds are rich in lysine, arginine, leucine, phenylalanine and glutamic acid. The antioxidative effect of roselle seed extract increases when combined with other antioxidant compounds compared to when used alone. The protein quality of roselle seed powder prepared from dried and boiled seeds is similar. Roselle seeds were also reported to possess anti-hypercholesterolemia effects tested using an animal model. To exploit the seeds which contain high value health-promoting components as functional ingredients, their possible application in food products should be studied.