Retroviral reverse transcriptase inhibitory activity in Thai herbs and spices: screening with Moloney murine leukemia viral enzyme.
Fifty-seven Thai herbs and spices were examined for their retroviral reverse transcriptase inhibitory activity. All herbs and spices were extracted with hot-water and methanol. Reverse transcriptase inhibitory activity of the extracts was determined using Moloney murine leukaemia virus reverse transcriptase (M-MuLV-RT) reacted with 3H-dTTP. Of the hot-water extracts, 81% (46/57) showed inhibitory activity compared with 54% (31/57) of the methanol extracts. At a concentration of 125 µg/ml, 13% (6/46) of hot-water extracts, namely Eugenia caryophyllus [Syzygium aromaticum], Phyllanthus urinaria, Terminalia belerica [T. bellirica], Nelumbo nucifera, Psidium guajava, and Lawsonia inermis, had a relative inhibitory ratio (IR) >50% (100, 91, 75, 74, 61 and 60%, respectively). For the methanol extracts, only 10% (3/31) had IR values >50%. They were T. belerica, E. caryophyllus and N. nucifera which exhibited IR values of 83, 54 and 54%, respectively.