Isoteoline is a compound of aporphine structure derived from the alkaloid glaucine. Previous studies with isoteoline have shown antagonistic activity at 5-HT(2C) serotonergic receptors. We have investigated whether isoteoline interacts with 5-HT(1B) receptors. An isolation-induced social behavioural deficit test in mice was used as a model of stimulation of these receptors. The deficit in the behaviour of isolated mice in this experimental procedure was reported to be sensitive to 5-HT(1B)-receptor stimulation, since agonists at these receptors are capable of reversing it. In our study, we used N-(3-trifluoromethylphenyl)piperazine (TFMPP) (2 mg kg(-1)) as a reference agonist at these receptor sites. TFMPP completely restored the normal behaviour of the isolated mice. Its effect was prevented by propranolol (4 mg kg(-1)), a beta-adrenergic receptor antagonist with a high affinity for 5-HT(1B) receptors, which was inactive by itself. When isoteoline was given before TFMPP, it did not prevent the effect of the latter. Given alone at doses of 0.25, 1, 4 or 8 mg kg(-1), isoteoline showed an effect of its own to normalize the behaviour of isolated mice. The effect of isoteoline (1 mg kg(-1), i.p.) was antagonized by pretreatment with propranolol, indicating that it was mediated through stimulation of 5-HT(1B) receptors. Repeated treatment with isoteoline (1 mg kg(-1), 2 x 3 days, i.p.) produced tolerance to its effect and significantly attenuated the effect of TFMPP, when animals were tested 16 h after the last injection. In conclusion, the results provided functional evidence of agonist-like activity of isoteoline at the 5-HT(1B) receptors.

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In recent years much attention has been focused on the pharmaceutical relevance of bioflavonoids, especially hesperidin and its aglycon hesperetin in terms of their antioxidant and anti-inflammatory actions. However, the bioactivity of their metabolites, the real molecules in vivo hesperetin glucuronides/sulfates produced after ingestion, has been poorly understood. Thus, the study using an ex vivo approach is aimed to compare the antioxidant and anti-inflammatory activities of hesperidin/hesperetin or hesperetin metabolites derived from hesperetin-administered rat serum. We found that hesperetin metabolites (2.5-20 μM) showed higher antioxidant activity against various oxidative systems, including superoxide anion scavenging, reducing power, and metal chelating effects, than that of hesperidin or hesperetin. The data also showed that pretreatment of hesperetin metabolites (1-10 μM) within the range of physiological concentrations, compared to hesperetin, significantly inhibited nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production, as evidenced by the inhibition of their precursors, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels without appreciable cytotoxicity on LPS-activated RAW264.7 macrophages or A7r5 smooth muscle cells. Concomitantly, hesperetin metabolites dose-dependently inhibited LPS-induced intracellular reactive oxygen species (ROS). Furthermore, hesperetin metabolites significantly downregulate LPS-induced nuclear factor-κB (NF-κB) activation followed by the suppression of inhibitor-κB (I-κB) degradation and phosphorylation of c-Jun N-terminal kinase1/2 (JNK1/2) and p38 MAPKs after challenge with LPS. Hesperetin metabolites ex vivo showed potent antioxidant and anti-inflammatory activity in comparison with hesperidin/hesperetin.

Baicalin, baicalein, wogonoside and wogonin are flavone constituents of Scutellariae Radix with various beneficial biological activities. The purpose of this study was to investigate the urinary pharmacokinetics of these flavones after oral administration of Scutellariae Radix commercial powder. Ten healthy male volunteers received a dose of 5.2 g commercial powder (comparable to 9 g crude drug), respectively. The concentrations of baicalin, baicalein and wogonin in the commercial powder as well as their metabolites in urine were assayed by HPLC method. The glucuronides and sulfates of baicalein and wogonin in urine were hydrolyzed with b b-glucuronidase and sulfatase, respectively. Our results showed that the mean cumulated renal excretion of baicalein glucuronides and sulfates were 43.1؎4.5 m mmol (2.9% of dose) and 64.8؎6.3 m mmol (4.3% of dose), respectively, whereas wogonin glucuronides and sulfates were 21.6؎2.0 m mmol (5.9% of dose) and 20.7؎1.7 m mmol (5.7% of dose), respectively. The result indicated that the renal excretion of conjugated metabolites of wogonin (11.6% of dose) were higher than that of baicalein (7.2% of dose). The baicalein sulfates was predominant than the corresponding glucuronides, whereas wogonin sulfates was comparable to the corresponding glucuronides.

3,3',4',7-Tetrahydroxyflavone (fisetin) has shown various beneficial bioactivities. This study investigated the metabolism and pharmacokinetics of fisetin, 5-hydroxyflavone (5-OH-flavone), and 7-hydroxyflavone (7-OH-flavone) in male Sprague-Dawley rats. Blood was withdrawn via cardiopuncture and assayed by HPLC before and after hydrolysis with sulfatase and beta-glucuronidase. The results indicated that after intravenous administration of fisetin (10 mg/kg of bw), fisetin declined rapidly and fisetin sulfates/glucuronides emerged instantaneously. When fisetin (50 mg/kg of bw) was given orally, fisetin parent form was transiently present in serum only during the absorption phase, whereas fisetin sulfates/glucuronides predominated. The serum metabolites of fisetin showed less potent inhibition on 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced hemolysis than fisetin. Following oral administrations of 40 mg/kg of bw of 5-OH-flavone and 7-OH-flavone, the glucuronide of 5-OH-flavone and the sulfate/glucuronide of 7-OH-flavone were found in serum, whereas no traces of parent forms were detected. In conclusion, fisetin and 7-OH-flavone were rapidly and extensively biotransformed into their sulfate/glucuronide, whereas 5-OH-flavone was exclusively metabolized to glucuronide.