They have found evidence that ginsenoside Rb1 - one of the principal active components of ginseng - can cause abnormalities in rat embryos.
Their research is published today (Thursday 25 September) in Europe's leading reproductive medicine journal Human Reproduction.
Dr Louis Chan and colleagues at the Chinese University of Hong Kong Prince of Wales Hospital, Hong Kong, tested ginsenoside Rb1 in various concentrations on 9-day old rat embryos.
They found that embryos exposed to more than 30 micrograms per millilitre of ginsenoside Rb1 had significantly lower morphological scores. Morphological scores are a way of assessing the development of the important organs of embryos: the higher the score, the more normal is the development of the embryo.
At 30 micrograms the total morphological scores were significantly lower than the scores of the control group, which had not been exposed to gensinoside - 35 as opposed to 45 - and they had lower scores for heart, limbs, eye development and flexion. At the highest dose of 50 micrograms the total score fell to 28 and the embryos were also significantly shorter in body length and had fewer somites (muscle pre-cursor cells).
"Our study has demonstrated that ginsenoside exerts a direct teratogenic effect on rat embryos: that is to say it is capable of causing malformations in rat embryos," said Dr Chan.
"Although there are numerous reports in the literature concerning the potential benefit of ginseng, much less is know about the potential toxicity and there are no data about its potential effect on the developing human foetus. Yet a survey published in 2001 showed that over 9% of pregnant women report using herbal supplements, and in Asia up to 10% have taken ginseng during pregnancy," he said.
Dr Chan said that in many countries herbal medicines such as extract of ginseng are placed on the market as food supplements and are available over the counter. Manufacturers are not required to submit proof of safety and efficacy before marketing.
He said that their study showed that the reduction in morphological score was dependent on the dose. It was therefore possible that lower concentrations of ginsenoside Rb1 might have caused less severe abnormalities that escaped detection by their research assessments, which were designed to study only gross abnormalities.
Ginsenoside Rb1 is only one of the ginsenosides in commercially available ginseng. More than 20 had been identified and previous studies had shown that different ginsenosides might have different actions. Dr Chan said that more studies were needed to evaluate the potential teratogenic effects of other ginsenosides.
"Although results from animal teratogenicity studies may not reflect the circumstances in humans, our findings suggest that further investigations and monitoring of embryonic effects of ginsenoside on human pregnancy are warranted," he said.
Ginseng, according to Dr Chan, is used to enhance stamina and the capacity to cope with fatigue and physical stress. It is also believed to have an anti-cancer function and to improve cognitive and physical performance. "So, pregnant women might take ginseng because they think it is good for their pregnancy and may not be aware that there could be unknown harmful effects."
He warned: "Before more information in humans becomes available, women should be cautious about using ginseng in the first three months of pregnancy and it is always advisable for pregnant women to consult their doctor before taking any herbal supplement."
Dr Chan added that a recent survey he had done showed that 55% of women in Hong Kong took traditional Chinese herbal medicine in pregnancy. The most common reasons for their use was that the women believed they were good for pregnancy and the foetus and good for their general health.
 An in-vitro study of ginsenoside Rb1 -induced teratogenicity using a whole rat embryo culture model. Human Reproduction. Vol 18. No 10 pp 2166-2168.
1 PDF version of this press release and full embargoed text of the paper with complete results can be found from 09:00hrs London time Monday 22 September at http://www3.
2 Human Reproduction is a monthly journal of the European Society of Human Reproduction and Embryology (ESHRE). Please acknowledge Human Reproduction as a source. Dr Helen Beard, Managing Editor. Tel: +44 (0) 1954 212404 Email: firstname.lastname@example.org
3 ESHRE's website is: http://www.
4 Abstracts of other papers in ESHRE's three journals: Human Reproduction, Molecular Human Reproduction & Human Reproduction Update can be accessed post embargo from http://www3.
Full text of papers available on request from Margaret Willson.
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