The present invention is directed to analogs of baicalein according to formula (I): where R5 is H, (C1-C12)alkyl, (C2-C13)acyl, or an optionally substituted phenyl or benzyl group, an acyl group, a C1-C20 alkyl or ether group, a phosphate, diphosphate, triphosphate or phosphodiester group; R6 and R7 are each independently H, (C1-C12)alkyl, (C2-C13)acyl, or an optionally substituted phenyl or benzyl or together form a —OCR1R2O— group wherein each of R1 and R2 is independently H, a C1-C3 alkyl group or an optionally substituted phenyl or benzyl group; and R8 is H, OH, an O-acyl group, a C1,-C4 alkyl or alkoxy group, F, Cl, Br or I, or a pharmaceutically acceptable salt thereof, which exhibit anti-P-glycoprotein activity and methods of enhancing the bioavailability of active compounds, especially orally administered compounds, by inhibition of P-glycoprotein 170 (P-gp 170) and/or CYP450 enzyme, especially CYP450 3A4 enzyme. Pharmaceutical compositions based upon these novel derivatives according to the present invention are also described herein.