Two herbs used as folk therapy contraceptives could offer hope to millions of women who struggle with the side effects of the Pill.

The chemicals, found in aloe vera and thunder god vine block a key step in fertilisation, a study has found.

Extracts from the plants could provide the basis of a new kind of non-hormonal "molecular condom" which could be taken before or after sex to prevent conception.

In the folk medicine tradition, aloe vera and thunder god vine are both claimed to prevent unwanted pregnancies, as well as having other beneficial effects.

Scientists identified two molecules - lupeol from aloe vera and pristimerin from thunder god vine - that in laboratory tests prevented sperm breaking through a protective "wall" of cells surrounding the egg.