Objectives:The effects of two humate products were compared to that of prednisolone on a contact hypersensitivity rat model. Methods: Rats, sensitized with dinitrofluorobenzene (DNFB), were placed on a daily oral treatment of 61mg/kg BW of humate derived from either leonardite or bituminous coal or on prednisolone at one mg/kg BW and challenged 6 days later with a topical application of DNFB to the right ear. The inflamed ears were measured daily. In a toxicity study rats were exposed to daily oral treatment of leonardite humate at 1,000 mg/kg BW for 1 month. A teratogenicity study was done where pregnant rats were treated with 500 mg/kg BW on days 5 to 17 of pregnancy. Results: Only the leonardite humate compared favourably with prednisolone in suppressing contact hypersensitivity. No signs of toxicity were observed and weight gain was normal during the 6-day and 1month treatments and during the teratogenicity study with the leonardite humate. However, the rats on the other two products experienced slower weight gain. Conclusion: The identification of a naturally occurring nontoxic compound with anti-inflammatory activity is exciting and merits further evaluation in the treatment of patients suffering from inflammatory conditions.

Abstract:A. venosum and B. micrantha are widely used ethnomedically and B. micrantha has furthermore indicated the potential to be developed into a drug due to the various biological activities previously reported. However, the safety of a plant must be determined before drug development. Cytotoxicity was determined using human adenocarcinoma cells of the cervix (HeLa), human breast cells (MCF-12A), lymphocytes (both resting and stimulated) as well as primary porcine hepatocytes. Acute systemic toxicity was determined using the luminescent bacteria, Vibrio fischerii and the vertebrate, Poecilia reticulata (guppy). Toxicity was found to be concentration dependent when HeLa and MCF-12A cells were exposed to the plant extracts. The IC 50 was not reached at the concentrations tested (0.1 μg/ml -1 mg/ml) for the hepatocytes as well as the resting and stimulated lymphocytes, indicative that both plant extracts showed little or no direct cytotoxicity against primary cultures. Both extracts resulted in 100% mortality of the guppies. This study illustrated that extracts of both B. micrantha and A. venosum are cytotoxic and possess acute systemic toxicity.