Context: Anti-inflammatory drugs and biologics can effectively treat inflammatory conditions and diseases but can also cause burdensome side effects. Many patients prefer to use time-tested, traditional medicinal products and dietary supplements, but such products seldom receive the rigorous testing required for regulatory approvals of drugs and biologics. Thus, it is advantageous to demonstrate by experimentation the pharmacological and toxicological properties of unapproved natural products and compared to benchmark approved drugs or biologics.
Objective: The studies intended to evaluate Samento®, a commercial hydro-alcoholic extract of the pentacyclic chemotype of Uncaria Tomentosa (Willd.) DC, for the prophylactic and treatment effects of irritant-induced inflammation and antigen-induced arthritic inflammation in two rat models. The studies were also intended to create a clinical bridge rationale for the use of Samento® in the treatment of inflammation in humans, with a suggested allometrically scaled starting dose.
Design: The research team performed two in vivo animal model studies of induced inflammation in rats.
Setting: The studies took place at the Universidad Peruana Cayetano Heredia in Lima, Peru.
Prophylaxis model of irritant-induced inflammation: Holtzman rats in five groups (five each per group) were administered 14 daily doses of Samento® at 250, 500, and 1000 mg/kg of wet weight, or 40 mg/kg of naproxen sodium as a positive control, or nothing as a negative control. At 14 days the right legs of the rats were challenged by injection into the connective tissue by the chemical irritant carrageenan. Two hours thereafter the weight of the irritant-injected right leg was compared to the non-injected left leg of each rat, to determine the level of irritant-induced inflammation.
Treatment model of antigen-induced arthritic inflammation: Arthritic inflammation was induced in five groups of Lewis rats (five each per group) by intradermal injection of the tail with non-allogeneic, bovine type II collagen in incomplete Freund's adjuvant. A sixth group was not injected with collagen antigen as a non-induced control. Ten days after the induction of arthritic inflammation in the five injected groups, individual groups were treated with Samento® at 250, 500, and 1000 mg/kg of wet weight daily for 21 days, or 0.2 mg/kg of methotrexate twice per week as a positive control, or nothing as a negative control. At 21 days the animals were assessed for antigen-induced arthritic inflammation and assigned an analog score ranging from 0 to 4.
Results: The research team confirmed the presence of pentacyclic oxindoles and the absence of tetracyclic oxindoles within Samento®. In the prophylactic model, 14 days of pretreatment with oral Samento® produced dose-dependent, statistically significant reductions in inflammation in the rats' leg weights between the carrageenan induction and postintervention, for the 250, 500, and 1000 mg/kg Samento® groups (P < .05 for all groups). The 1000 mg/kg group had a 74% anti-inflammatory effect versus 97% with the 40 mg/kg of naproxen sodium in the positive control group. In the treatment model, 21 days of oral administration of Samento® produced dose-dependent, statistically significant reductions in arthritic inflammation postintervention, for the 250, 500, and 1000 mg/kg Samento® groups (P < .05 for all groups). Treatment with the highest tested dose of the extract (1000 mg/kg) yielded an 85% anti-inflammatory effect versus 90% with 0.2 mg/kg of methotrexate in the positive control group.
Conclusions: The two rat models revealed that the Uncaria phytotherapy Samento® was an effective prophylactic as well as a treatment for induced inflammation in rats. The highest dose of the pentacyclic chemotype of Uncaria approached the anti-inflammatory activities of the established benchmark pharmaceutical positive controls. The results in the two rat models suggest an allometrically scaled starting dose of Samento® of 4 g daily in humans.
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