Comparative antioxidant-capacity and -content of leaves, bulbs, roots, flowers and fruit of Gethyllis multifolia L. Bolus and G. villosa Thunb. species

The total polyphenol, oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP), radical cation scavenging ability, flavonol and flavanone contents were measured in the leaves, bulbs, roots, flowers and fruit (dry weight) of two natural populations of Gethyllis multifolia (Kukumakranka) and Gethyllis villosa. The flowers and fruit of G. multifolia and G. villosa showed higher, and in some cases significantly (P < 0.05) higher antioxidant activities when compared to the leaves, bulbs and roots. This, however, was not true for the flavanone content in both species. The total polyphenol content in the fruits of G. multifolia (21.54 mg GAE/g) and G. villosa (27.64 mg GAE/g) were found to be in agreement with those of raisins (28.30 mg GAE/g), blueberries (24 mg GAE/g) and strawberries (15.40 mg GAE/g). The FRAP values of G. multifolia flowers (76.66 μmole AAE/g) and fruit (91.51 μmole AAE/g) were found to be significantly (P < 0.05) higher than those of the other plant parts (16.76 to 39.08 μmol AAE/g). On the other hand, the flowers (590.23 μmol TE/g) and fruit (741.16 μmol TE/g) of G. villosa revealed a significantly (P < 0.05) higher ORAC when compared to the other plant parts (251.25 to 410.60 μmol TE/g). A strong correlation was evident in the fruit of both species between the total polyphenols and FRAP (r = 0.95), ORAC (r = 0.95) and flavonol content (r = 0.79).

Research Highlights
► We worked on two South African bulbs of which on is threatened.
► The fruit and flower of both species is said to have medicinal properties.
► No antioxidant research work has been done on the fruit of these two species.
► Flowers and fruit showed higher antioxidant activity compared to other plant parts.
► The polyphenol content of the fruit was in line with some commercial fruits.