The present invention is related to a "bioactive" composition that comprisesone or more oligogalacturonans((1→ 4)-α-D-galacturonan) orany other oligosaccharides (oligoguluronans) that may present an "egg box"conformation, this conformation being further stabilized by one or more polycationicsaccharide(s), preferably either a chitosan oligosaccharide or a chitosanpolysaccharide. The present invention is also related to a method for the preparationof this composition and its use, in medical, pharmaceutical, agricultural,nutraceutical, food, feed, textile, cosmetic, industrial and/or environmentalapplications.