Isolation of betulinic acid and antioxidant and anti-HIV-1 reverse transcriptase activity of Cratoxylum formosum subsp. pruniflorum (Kurz) Gogelein extract

Abstract

Cratoxylum formosum subsp. pruniflorum (Kurz) Gogelein has been used as a medicinal plantfor the treatment of many diseases. C. formosum bark was macerated with methanol and partitionedusing hexane and chloroform. The chloroform bark extract was fractionated using columnchromatography. Five combined fractions were obtained (CFA–CFE) and then investigated forantioxidant activity based on the total phenolic content (TPC), total flavonoids content (TFC),ferric reducing antioxidant power (FRAP) and nitric oxide (NO) radical scavenging activity andalso for anti-HIV-1 reverse transcriptase (RT) activity. CFE had the highest antioxidant activity,with values for TPC, TFC and FRAP of 44.84 ± 0.05 μg of gallic acid equivalents/g,580.69 ± 0.78 μg of quercetin equivalents/g and 82.56 ± 0.08 μg of Trolox equivalents/g of dryweight extract, respectively, and CFB inhibited the nitric oxide radical at the lowest concentration(96.73 μg/mL). However, the methanolic bark extract, fractions CFC, CFD and CFE had highinhibitory effects against HIV-1 RT with values greater than 60% relative inhibition. CFE hadthe highest percentage relative inhibition among the fractions and was at a comparable level toa standard drug (Nevirapine). The ranking of the antioxidant and anti-HIV-1 RT activities of thefractions was CFE followed by CFD, CFC, CFB and CFA, respectively. Betulinic acid was isolatedfrom fraction 52 of the chloroform extract that was eluted with chloroform-acetone (1:9, volumeper volume). The 1H and 13C nuclear magnetic resonance data obtained were in accordance withthe previous published data. There is a need for further isolation of bioactive compounds andevaluation of their antioxidant and anti-HIV activities.