Synergistic, Additive, and Antagonistic Effects of Herbal Extracts

When herbs are combined in mixtures or formulas, the chemical characteristics of the overall mixture can change, increasing or decreasing the availability and effects of some of the constituents.

Traditional Chinese medicine (TCM) combines herbs within formulas, taking into consideration the synergistic, additive, and antagonistic effects among the constituent herbs. This practice is also common in other herbal systems, such as in Central and South America, where many health conditions are treated with bottled herbal mixtures called botellas (in Spanish-speaking countries) or garrafadas (in Portuguese-speaking countries).

Advancements in analytical and synthetic chemistry now make it possible to better understand the potential effects of drug combinations on a living system. Scientists are exploring the dose-effect relationships (the change in effect caused by different dose levels) of each drug alone and in combinations to determine whether a given drug or herbal mixture would have an additive, synergistic, or antagonistic effect.

An additive interaction means that the effect of two chemicals taken together is equal to the sum of the effect of the two chemicals taken separately. Synergism, on the other hand, implies an effect that is more than additive — taken together, the two herbs have a greater effect. And antagonism is an effect that is less than additive — taken together, the herbs have a lesser effect.

A combination of herbs in a formula or mixture can target multiple areas of your body and a variety of conditions simultaneously. What’s more, combining multiple herbs that have different mechanisms of action also can provide more effective treatment against a disease.

Herbal Extracts

In the Dominican Republic, a traditional herbal preparation known as a botella contains different plant parts immersed in alcohol. The beverage is used to prevent and treat many health conditions.

Because of these plant interactions, herbal preparations offer several advantages: They can increase the efficacy of the therapeutic effect; they can reduce the chance of toxicity because less of each herb is needed to achieve the same result; and they can minimize or slow the development of drug resistance.

Addition and antagonism can also be used to perfect an herbal formulation. In a 2006 Yale Scientific article outlining the importance of integrating Western and Eastern medical practices to address unmet needs in “conventional” medicine, Yung-Chi Cheng, a professor at Yale Medical School, explained the interaction and roles of different herbs in TCM using the following metaphor:

The herbs in a typical TCM formulation . . . play different roles. Jun, the emperor herb, is the principal ingredient; chen, the minister herb, aids the jun often by augmenting or broadening its effects or by attending to secondary symptoms; zuo, the assistant, can moderate the activities of the jun and chen or also address secondary symptoms; finally, shi, the ambassador herb, aids in the absorption and transport of all the other herbs to their destinations. Thus, the herbs prescribed in a given formulation must work in concert to achieve a desired effect.