Synthesis of new series of pyrimido[4,5-b][1,4] benzothiazines as 15-lipoxygenase inhibitors and study of their inhibitory mechanism

A series of 2-substituted 4-n-propyl pyrimido[4,5-b][1,4]benzothiazines were synthesized, and evaluated as soybean 15-lipoxygenase (SLO) inhibitors. Among the synthesized compounds, 2-(4-methyl piperazinyl) analog showed the best SLO inhibition activity (IC50 = 8.9 +/- A 0.4 mu M). To rationalize the inhibitory potency variation of the compounds, computer-assisted modeling of the enzyme-inhibitor, radical scavenging evaluation, and inhibitory mechanism analyses were performed. The results showed that in 4-alkyl pyrimido[4,5-b]benzothiazines with same 2-substituent, radical scavenging potency plays a key role in lipoxygenase inhibition.