At this moment men have two options for contraception: the use of a condom to catch the sperm or to have a vasectomy – sterilizing operation which cut the two tubes that carry sperm to the penis from where they are made in the testicles. Condoms are not 100% reliable (failure rate of around 18%) and it is a short term solution, while a vasectomy is a permanent option and just some of men manage to successfully reverse the operation.

The most optimistic prospect is Vasalgel, which has shown to be effective in animal trials. Other seemingly promising alternatives have faced development barriers—last year, for instance, a groundbreaking study on a male contraceptive injection ended early because the participants couldn’t handle the annoying side effects, like mood swings and acne.

Contraceptive failure rates. Image credit: Centers for Disease Control and Prevention

Now, a group of researchers from the University of California – Berkeley have started testing out a new approach. They have found that two chemicals found in folk medicine can help block the fertilization of an egg and could make effective alternatives to hormone-based contraceptives.

Blocking CatSper Channels

CatSper channel known as calcium channel of sperm is vital for male fertility and it is activated by the progesterone hormone. Scientists have known about CatSper since 2001 when they stumbled across it while studying male infertility. The patients, it turned out, had a mutation in at least one of the nine genes that code for CatSper.

In this study, researchers screened more than 50 chemical compounds to find a few that could tightly bind with CatSper and block it. It turns out that the two compounds proved to be the best blockers. They found that concentrations of lupeol (a common molecule found in plants like olives, mangos, and grapes) could prevent calcium ions from giving sperm the boost it needs to penetrate an egg. The second compound is pristimerin used in traditional Chinese remedies to treat arthritis.

The female hormone progesterone (green) affects the CatSper ion channels (red) in the tail of the sperm, which then allow calcium ions (yellow) to flow into the sperm. Blocking progesterone activation could lead to a unisex birth control method. Image credit: Caesar Foundation

This study is still pre-clinical and researchers working currently on animal trial. If everything goes well, this method could lead to a unisex birth control method that works by blocking progesterone activation. For women, this could be a plan B, which would be effective before fertilization, or within six hours of sex. For men, it could work analogously to the pill.

Assistant professor of molecular and cell biology and study author Polina Lishko said that this could be a generation of emergency contraceptives which they nicknamed the molecular condoms.