Cover Image


View/Hide Left Panel

Summary of the conclusions: Although substantial limitations exist in the available information, concerns about the safety of chaparral remain based on the weight of the evidence discussed above. The most significant concern is hepatotoxicity, but some concerns also exist for reproductive and renal toxicities. This is especially applicable for certain groups, including those with pre-existing hepatic or renal problems, those taking drugs that affect liver function, those with current or prior alcohol abuse, and women of child-bearing age. There is more concern with ingestion of chaparral preparations containing leaves/stems or alcoholic extracts than with the ingestion of aqueous extracts (i.e., teas) because of the higher content of NDGA and other lipophilic compounds in the former preparations.

C. Data Gaps and Future Research Recommended

Concern for possible adverse effects in American Indian and Hispanic populations that use local botanical remedies prompts the panel to propose research needs that will help in the evaluation of the human clinical data. This concern would be increased if a resurgence in public interest in chaparral occurs.

Detailed toxicity studies in animals are needed to explore the possible dose-response relationship in the development of hepatotoxicity and nephrotoxicity as the result of chaparral ingestion. In animal studies, pair feeding should be included in the experimental protocol due to possible aversion to the chow if NDGA has been added (Goodman et al., 1970). Ideally, studies should compare the different preparations of chaparral (powdered leaf, alcoholic extract, and water extract). The differences in the chemical composition of the various preparations of chaparral need to be explored. The literature shows that a preponderance of toxicities were associated with preparations other than tea; hepatotoxicity was not reported in a clinical trial of cancer patients drinking chaparral tea. This suggests that there are differences in the bioavailability of the components of chaparral that result from differences in the chemical composition of the various preparations. These differences need to be explored in detail.

In all further research, it is important to carry out careful product characterization. A qualified taxonomist should identify the plant material and a botanical sample should be retained in an herbarium for future reference. It is important to carefully describe the plant part utilized. As an example, newer leaves should be distinguished from older leaves because newer leaves contain a higher proportion of the NDGA-containing resin. Chaparral roots contain a quinone not reported to be present in the aerial parts of the plants and, thus, roots should be carefully excluded. The plant material should be chemically profiled, including quantitative determina-

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement