Isolation and quantification of bioactive compounds from lesser galangal (Alpinia officinarum)

Lesser galangal (Alpinia officinarum) is of the Zingiberaceae family and Alpinia genus. Of the many compounds identified in lesser galangal, diarylheptanoids are among the most important. Recently several flavonoids and diarylheptanoids were isolated and characterized as COX-2 inhibitors.; This research involved bioassay-directed fractionation of lesser galangal, whose crude extracts were found to kill prostate cancer cell lines. Later work found that the cytotoxicity was related to restore cancer cells' sensitivity to apoptosis.; Bioassay directed fractionation of the ethyl acetate extract of lesser galangal rhizome yielded an active fraction when eluted with 30:1 chloroform/methanol, from which column chromatography and HPLC have led to the isolation of three flavonoids and five diarylheptanoids.; The bioassay was performed for the above eight compounds. The three flavonoids displayed no activity to induce apoptosis in prostate cancer cell Du-145 whereas the five diarylheptanoids all possessed the bioactivity. AO-7 was the most potent followed by AO-6 and AO-8 with the IC50 12.5, 20 and 32 muM, respectively.; The DPPH method has been used to evaluate the diarylheptanoids' free radical scavenging activity. The results showed that AO-1, AO-5 and AO-7 had potent activity to scavenge DPPH free radical with EC50 11.4, 12.7 and 13.7 muM, respectively whereas AO-6 and AO-8 displayed poor bioactivity. The diarylheptanoids' ability to scavenge hydrogen peroxide was following the same sequence as they scavenged DPPH.; A HPLC method has been developed for quantitation of the above five diarylheptanoids in three different samples. The contents of them are as following: the content of AO-1 is the highest followed by AO-8, AO-7, AO-6 and the content of AO-5 is the lowest. For electroactive compounds, electrochemical detection is about 100--200 times more sensitive than UV detection at 280 nm.