Hope for plant-based contraceptive, study claims


"Forget Plan B – try aloe vera, controversial study claims: Scientists insist pills made from dandelions and mangoes can prevent pregnancy without a hit of hormones," reports the Mail Online. The news is based on a study...

"Forget Plan B – try aloe vera, controversial study claims: Scientists insist pills made from dandelions and mangoes can prevent pregnancy without a hit of hormones," reports the Mail Online.

The news is based on a study investigating whether chemicals found in certain plants can reduce sperm's ability to fertilise a woman's egg.

Sperm get a boost of energy from the hormone progesterone as they approach the egg. This activation increases their swimming speed in the female reproductive tract, enabling them to penetrate the egg.

Using donor sperm samples, this research showed how two plant chemicals – pristimerin (found in thunder god vine) and lupeol (found in mango, dandelion root and aloe vera) – were able to prevent sperm activation.

This raises the possibility that these natural substances could act as an alternative to hormone-based contraceptives, which are known to have side effects.

More laboratory research is needed to show if this type of contraceptive method has the potential to be safe and effective before researchers can consider moving on to human trials.

The researchers are currently working on developing a contraceptive patch and pill. But it's likely to be many years before we know if this could lead to a new licensed contraceptive.

Where did the story come from?

The study was carried out by researchers from the University of California.

It was funded by a US National Institutes of Health grant, a Pew Biomedical Scholars Award, an Alfred P Sloan Award, and Packer Wentz Endowment Will.

The researchers declare a conflict of interest in that two of the authors are inventors on a patent application filed by the University of California.

The study was published in the peer-reviewed journal Proceedings of the National Academy of Sciences and is free to read online.

The news stories have broadly reported the story accurately, but don't state that any potential new contraceptive would take years to develop. 

What kind of research was this?

This laboratory study aimed to assess whether it's possible to use plant chemicals to restrict sperm movement, thereby preventing them from moving effectively towards the egg.

The researchers explain how the sperm calcium channel, CatSper, which is found in the tail, is a key part of male fertility.

The female hormone progesterone activates CatSper by binding to a particular receptor (ABHD2), energising the sperm and boosting fertility.

In theory, any chemical that blocks this receptor has the potential to behave like a contraceptive and prevent fertilisation.

This type of research is useful for further understanding how biological mechanisms work and identifying potential new therapies.

But even if it's shown to work in the laboratory, much more testing is needed before we can conclude that this is a safe and effective alternative form of contraception.  

What did the research involve?

Four healthy donors provided sperm samples for this research. The researchers analysed the effects different hormones and substances have on calcium channels (CatSper) and consequently sperm movement. All tests were performed at normal body temperature (37C). 

Sperm samples were exposed to the following hormones:

  • testosterone
  • oestrogen
  • progesterone
  • hydrocortisone (a steroid hormone)
  • pregnenolone sulphate (a steroid hormone)

What were the basic results?

The researchers found testosterone, oestrogen and hydrocortisone had no effect on the mobility of sperm and its ability to penetrate the egg.

They confirmed that progesterone activates the sperm for fertilisation by binding to the ABHD2 receptor. They also found pregnenolone sulphate had a similar effect in activating sperm, likely by binding to the same site.

The researchers then identified two steroid-like plant chemicals, pristimerin and lupeol, which appeared to block the action of the progesterone and pregnenolone sulphate on sperm.

By preventing the action of the other hormones, they reduced the sperm's ability to activate and then penetrate and fertilise an egg. 

How did the researchers interpret the results?

The researchers concluded that their results indicate pregnenolone sulphate and progesterone are the main steroids that initiate sperm activation.

Pristimerin and lupeol, found in plants, can act as contraceptives by reducing sperm movement and preventing fertilisation.  


This laboratory study aimed to investigate a variety of steroid hormones and plant compounds to look at their effect on sperm activation and ability to fertilise an egg.

The researchers confirmed that the hormone progesterone present in the female reproductive tract seems to be needed to activate sperm and make them able to fertilise an egg.

The also found that two plant compounds, pristimerin and lupeol, were able to block the sites on the sperm that are activated by progesterone. This means these two compounds could have a potential contraceptive action.

But it's far too early to say whether new contraceptives could become available as a result of this research. More laboratory research would be needed to show their potential to be safe and effective before considering trials in humans.

For example, at the current stage it's not actually known whether these compounds would incapacitate all sperm and prevent them fertilising an egg.

It's also unclear what method of exposure would be needed (like a pill, patch or vaginal ring) and whether the compounds have toxic side effects.

Most potential new treatments identified at such an early experimental stage don't make it all the way to becoming licensed treatments available to the general public. 

Find out more about contraception.

Article Metadata Date Published: Mo, 21 Aug 2017
Author: Zana Technologies GmbH
NHS Choices