Total phenols and antioxidant potential of Pelargonium reniforme Curtis and Pelargonium sidoides DC under different watering frequencies and arbuscular mycorrhiza applications

Abstract

Pelargonium reniforme Curtis and Pelargonium sidoides DC are medicinally important plants of the large family Geraniaceae and indigenous to the southern areas of Africa. Both species are small shrublets or sub-shrubs whose tuberous roots contain essential metabolites used for the treatment of several diseases. The efficacy of these two species has been well documented, especially, their antioxidant potential. In this study, the antioxidant activity and accumulation of polyphenols in the root tubers of both species cultivated under varying irrigation regimes and arbuscular mycorrhiza applications were assessed using the Folin-Ciocalteu’s (polyphenols), ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. The total phenols in the water frequency treatments were found to be significantly higher in P. sidoides compared to that of P. reniforme at P≤0.05. FRAP values of P. reniforme were found to be significantly higher in lower water frequency (P≤0.05) with mycorrhiza addition as compared to P. sidoides with no significance. The results showed that the addition of mycorrhiza improved the FRAP content in the dry root tuber material of P. reniforme. The water frequency, mycorrhiza and their interaction showed no significant difference in the ORAC values of both species. A strong correlation was evident in the lower water frequency treatments in both species between the total polyphenols and FRAP content.