natural-products-in-plant-pest-management

52 J.C. Pretorius and E. van der WattOther known sterols are cholesterol that acts as a precursor of othersteroids in plants, and ergosterol that is rare in plants but abundant in fungi(Fig. 3.10). Usually, if the ergosterol concentration increases in plants, it is anindication of fungal infection.Saponins are so-called triterpene-glycosides coupled to a sugar group.The molecule consists of two parts, namely the glycone (sugar) and aglycone(triterpene) moieties (Fig. 3.11). Saponins have soap properties, foam in waterand have a bitter taste. They are also known for their medicinal properties inAsiatic communities.OHCH 3OHHOHOOH OFig. 3.9. A typical brassinosteroid (brassinolide).HOHOCholesterolErgosterolFig. 3.10. Two known sterols, cholesterol and ergosterol.AglyconeHOHHOSugarOOHHCH 2 OHOHOFig. 3.11. A typical saponin.