Variations of Carotenoids, Total Bioactive Contents, and Antioxidant Activity in Leaves of Medicago polymorpha

Abstract

Medicago polymorpha L. (MP) is a herbaceous plant commonly known as “bur clover.” It is aboriginal to Central and Western Asia and extensively distributed around the world. This study determines the changes in carotenoids and antioxidant potential of different MP of different origins. The sample leaves were analyzed for identification and quantification of carotenoids using a reversed-phase HPLC system. The result showed nine carotenoids and pigments in each sample. The major carotenoid compounds were phytoene, phytofluene, neoxanthin and its isomer (9-Z-neoxanthin), violaxanthin, lutein along with their isomers (9-Z-lutein, 9′-Z-lutein), and all-E-β-carotene. The major pigments were 15-hydroxy-lactone chlorophyll a, pheophytin a, pheophytin a′, pyropheophytin a, divinyl chlorophyll a, chlorophyll b′, chlorophyll b, 13′-hydroxy-lactone chlorophyll b, and hydroxy pheophytin a′. The carotenoids were detected in considerable amounts in the samples from Lower Dir (213 μg/g), Swat (171 μg/g), and Buner (157 μg/g). Chlorophylls were higher in Lower Dir (203.4 μg/g), Swat (184.0 μg/g), and Buner (152.2 μg/g) and significantly lower amounts in Malakand samples (141.7 μg/g). The total carotenoids in Lower Dir (51.2%) were higher than in Swat (48.2%), Buner (50.8%), and Malakand samples (44.6%). The amounts of violaxanthin and lutein were significantly higher in Lower Dir (73.6%) samples, followed by Malakand (51.7%), whereas Buner and Swat samples showed the lowest levels. In conclusion, MP leaves are a good source of important carotenoids having potential antioxidant properties, which are highly correlated to the violaxanthin and lutein contents.