Molecular contraception
Scientists have obtained a contraceptive from dandelion root
Molecular biologists from the USA have shown that two compounds that occur, for example, in aloe, mango and dandelion roots, prevent the sperm from fertilizing the egg. It may be possible to create safe contraceptives based on them.
Polina Lishko and her colleagues from the University of California at Berkeley found out that pristimerin and lupeol – compounds from the group of triterpenoids – prevent spermatozoa from "accelerating" and getting the impulse necessary to penetrate the egg through the elastic shell around it.
Drawing from the UC Berkeley press release
Folk contraceptives lead researchers to drugs that block fertilization – VM.
Lupeol is found, for example, in mango and dandelion root, and pristimerin is obtained from the three-winged Wilford (Tripterygium wilfordii), a Far Eastern plant whose leaves are used in traditional Chinese medicine to treat rheumatoid arthritis and as a way to prevent pregnancy.
According to the researchers, the compounds they found can work as emergency contraception before or after sexual intercourse or as a permanent one – for example, in the form of a patch or a vaginal ring. In addition, since they prevent fertilization, pristimerin and lupeol can be considered as an ethically preferable alternative to emergency contraception based on levonorgestrel (postinor or American Plan B drugs), which does not allow an already fertilized egg to gain a foothold in the uterus.
"Since these two plant compounds block fertilization at extremely low concentrations – about 10 times lower than the levonorgestrel content in the Plan B tablet – they can become a new generation of emergency contraception, which we call "molecular condoms". If we can use a non–toxic and non-hormonal compound of plant origin in a small concentration to prevent fertilization of the egg, this may become the best alternative to available contraceptives," said Lishko, whose words are quoted by the press service of the university.
Pristimerin and lupeol are not toxic to spermatozoa: they block the receptor protein that opens the CatSper calcium channel. As the Lishko group found out a year ago, it is the opening of this channel under the influence of progesterone that "switches" the spermatozoa from normal mobility to hyperactivity mode, thanks to which they penetrate through the shell around the egg.
Now scientists have found out that in addition to progesterone, the neurosteroid pregnenolone sulfate acts in a similar way on spermatozoa. At the same time, testosterone and cortisol in concentrations that can occur in the human body, on the contrary, blocked the "switching of speed" – this is how, scientists believe, stress and high testosterone levels in a woman can reduce fertility.
Now the researchers plan to test whether pristimerin and lupeol work on other primates – so far they have used human sperm in laboratory studies. In addition, the Lishko group will have to find possible ways to obtain compounds in industrial quantities, since it will be economically unprofitable to extract them from wild plants.
A study by Mannowetz et al. Regulation of the sperm calcium channel CatSper by endogenous steroids and plant triterpenoids is published in the journal Proceedings of the National Academy of Sciences.
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16.05.2017