Pharmacokinetic and metabolic studies of retrojusticidin B, a potential anti-viral lignan, in rats.

The pharmacokinetics and metabolism of retrojusticidin B, an anti-HIV reverse transcriptase agent isolated from Phyllanthus myritifolius, were studied in rats. The phase II conjugated metabolites were characterized after solvolysis and enzymatic hydrolysis. The oral bioavailabilities of retrojusticidin B, suspended in Tween 80 and in corn oil, were found to be 22.1% and 33.1%, respectively. The elimination half-lives (T1/2) were 22.9 and 36.2 minutes, respectively. The T1/2, clearance, and the volume of distribution (Vz) of retrojusticidin B estimated from i.v. measurements were 24.5 min, 2.6 +/- 0.4 L/min, and 90.6 +/- 6.4 L, respectively. 9,9'-Secoretrojusticidin B was shown to be phase I metabolite.