The invention relates to a family of oligopeptides with a completely new structure which occurs in selectively obtained royal jellies of certain vegetable origin and has been correlated with marked antiviral properties. The pilot structure is a molecule with 52 amino acids. Numerous analogous, nearly identical molecules are present in a satellite-like manner. The substances have a broad spectrum of antiviral activity, including against retroviruses, and have no toxic effect on humans even at high doses. A further surprising characteristic is their extreme resistance to all controlled proteases and other enzymes. The molecules are highly convoluted and resistant to attack. Despite their convolution they are geometrically very flexible and can form several conformers. The native state is easily soluble in water. Chemical synthesis results in a water insoluble form which can, however, be easily transformed into a soluble bioactive conformer which is similar to the native form. These new oligopeptides are therefore the first to combine in an optimal manner all the properties required of a potentially antiviral substance category.