Baicalein, a flavonoid extracted from a methanolic extract of Oroxylum indicum inhibits proliferation of a cancer cell line in vitro via induction of apoptosis.

A methanolic extract of the fruits of Oroxylum indicum, which is widely used in traditional Chinese herbal medicine for its anti-inflammatory, anti-pyretic and anti-hypersensitivity effects, inhibited in vitro proliferation of HL-60 cells. The flavonoid baicalein was found as an active component in the extract. Analysis of freeze-dried fruits of the plant indicated that this component comprised about 4% of the material by dry weight. In this study, we investigated the in vitro effects of baicalein on the viability and induction of apoptosis in the HL-60 cell line. The cell viability after treating with baicalein for 24 h was quantified by counting viable cells using trypan blue staining. The results showed that baicalein caused a 50% inhibition of HL-60 cells at concentrations of 25-30 microM. The inhibition of proliferation of HL-60 cells due to 36-48 h exposure to 10 or 20 microM baicalein was associated with the accumulation of cells at S or G2M phases. However, proliferation inhibition at a higher dose may be associated with induction by apoptosis, as evidenced by the typical nuclear fragmentation using DNA fragmentation assay and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The results indicate that baicalein has anti-tumor effects on human cancer cells, and Oroxylum indicum extract could be used in supplementary cancer therapy.

Structural analysis of a novel antimutagenic compound, 4-Hydroxypanduratin A, and the antimutagenic activity of flavonoids in a Thai spice, fingerroot (Boesenbergia pandurata Schult.) against mutagenic heterocyclic amines.

Six compounds were isolated from fresh rhizomes of fingerroot (Boesenbergia pandurata Schult.) as strong antimutagens toward 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) in Salmonella typhimurium TA98. These compounds were 2',4',6'-trihydroxychalcone (pinocembrin chalcone; 1), 2',4'-dihydroxy-6'-methoxychalcone (cardamonin; 2), 5,7-dihydroxyflavanone (pinocembrin; 3), 5-hydroxy-7-methoxyflavanone (pinostrobin; 4), (2,4,6-trihydroxyphenyl)-[3'-methyl-2'-(3' '-methylbut-2' '-enyl)-6'-phenylcyclohex-3'-enyl]methanone (5), and (2,6-dihydroxy-4-methoxyphenyl)-[3'-methyl-2'-(3' '-methylbut-2' '-enyl)-6'-phenylcyclohex-3'-enyl]methanone (panduratin A; 6). Compound 5 was a novel compound (tentatively termed 4-hydroxypanduratin A), and 1 was not previously reported in this plant, whereas 2-4 and 6 were known compounds. The antimutagenic IC(50) values of compounds 1-6 were 5.2 +/- 0.4, 5.9 +/- 0.7, 6.9 +/- 0.8, 5.3 +/- 1.0, 12.7 +/- 0.7, and 12.1 +/- 0.8 microM in the preincubation mixture, respectively. They also similarly inhibited the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). All of them strongly inhibited the N-hydroxylation of Trp-P-2. Thus, the antimutagenic effect of compounds 1-6 was mainly due to the inhibition of the first step of enzymatic activation of heterocyclic amines.

Antimutagenic activity against trp-P-1 of the edible Thai plant, Oroxylum indicum vent.

A methanolic extract of Oroxylum indicum strongly inhibited the mutagenicity of Trp-P-1 in an Ames test. The major antimutagenic constituent was identified as baicalein with an IC50 value of 2.78+/-0.15 microM. The potent antimutagenicity of the extract was correlated with the high content (3.95+/-0.43%, dry weight) of baicalein. Baicalein acted as a desmutagen since it inhibited the N-hydroxylation of Trp-P-2.