Use of Poor Qual­ity, Unstandardized Herbal Drugs

Read this article to learn about Consequences of the Use of Poor Qual­ity, Unstandardized Herbal Drugs.

The first obvious consequence of poor quality herbal medicines is that they will have no effica­cy or variable efficacy, and in some cases toxicity. This will result in loss of confi­dence in these products by the public and loss of sales. As has been stated before, there is now a strong feeling that some clinical testing of the most widely used herbal medicines should be carried out to provide scientific support for their use.

In­deed clinical trials have been conducted over the last few decades, but unfortunately the results have often been contradictory. One reason for this is the fact that the products often used in these trials were of poor quality, with unstandardized levels of active constituents.

For example, Ginger (Zin­giber officinale) is widely used as a spice, but also as an herbal medicine for treating pregnancy-related nausea and vomiting.

A recent systematic review of six double-blind, randomized controlled trials has shown that gin­ger may be effective in treating pregnancy-related nausea and vomiting.

However, other studies have shown that ginger is not effective in the treatment of postoperative nau­sea, motion sickness, or nausea of other etiology.

The factors contributing to the variability in clinical response to ginger are not known, but could be due to differences in the quality of the ginger products used, or to differ­ences in the composition of the ginger powders and ginger extracts used in the studies.

If ginger is to be used successfully as an herbal medicine, the composition of its major components will have to be determined and standardised. None of the gin­ger powders or extracts used in previous clinical studies was analysed prior to use and this repre­sents a major limitation of the studies.

Wolsko et al., (2005) have recently carried out a systematic and detailed assessment of the extent to which published randomized controlled trials of herbal medicines between the years 2000 – 2004 had characterised and verified the levels of active constituents of the herbal medicine un­der study.

They selected published English lan­guage randomized controlled trials evaluating sin­gle herb preparations of Echinacea, Gingko, Saw palmetto and St. John’a wort.

Of the 81 rand­omized trials they carefully examined, only 15% (12) reported performing tests to quantify actual contents, and 4% (3) provided adequate data to compare actual with expected content values of at least one chemical constituent.

Numerous stud­ies have demonstrated that marketed herbal med­icines are very often of poor quality, with variable levels of active constituents (see section 3.4). The use of such products in clinical trials has, not sur­prisingly, led to irreproducible and contradictory results.

However, nowadays more and more empha­sis is being put on the use of standardised materi­als in clinical trials.

For example, a systematic re­view of Andrographis paniculata for the treatment of upper respiratory infection (URI) by the Natu­ral Standard Research Collaboration (2006) found that the majority of these clinical trials were car­ried out using the product standardised to contain 5.25 mg andrographolide and de-oxy-andrographolide per tablet.

The results of these trials col­lectively suggest that this herb is effective in re­ducing symptom severity and duration in URI, both in children and adults, provided that the treatment is started within 36 to 48 hours of the onset of symptoms.

Standardised extract should also always be used in laboratory investigations for any particu­lar pharmacological activity, so that data between different laboratories can be compared. For ex­ample a recent investigation of the antioxidant activity of the leaves of Mangifera indica, utiliz­ing standardised extracts, has resulted in the iden­tification of very potent antioxidant activity in this plant.

The standardised ethanolic and aqueous extracts of M. indica leaf prepared to contain mangiferin concentration of 73 ± 0.17 mg/g of dry weight of the extract had free radical scavenging activity (IC₅₀) of 0.17 ± 0.02 mg/ml, and total phe­nolic content of 590 ± 48 mg/g of extract.

The protection exhibited by these extracts against lip­id peroxidation was superior to butylated hydroxytoluene and commercial grape seed extract.

Methods for good quality control and stand­ardisation are now available for many of the most commonly used herbs, and it is hoped that future studies are carried out on these standardised ex­tracts or formulated products. Scientific journals are becoming strict on publication of basic inves­tigations and clinical trials that have used unstandardized or poor quality herbal products.