Terpenoid Diversity in Sunflower ( Helianthus Annuus L.) and Their Potential in Crop Protection

Every year, more than 50 million tons of Helianthus annuus L. are produced mainly for the sunflower oil industry. It is a plant consumed worldwide, due to its use in feeding and traditional medicine for the prevention of some cardiovascular diseases, as anti-inflammatory, antimicrobial, antioxidant and antihypertensive, among others. Sunflower has a great diversity of metabolites, being especially rich in terpene compounds with close to 400 different molecules reported, including volatile mono and sesquiterpenes. Among these terpenic components of sunflower, sesquiterpenes as helibisabonols, helianuols and heliangolides, diterpenes (ent-kaurenes or ent-trachylobanes and ent-atisarenes compounds) or apocarotenoids (ionone compounds and strigolactones) are worthy to be underlined. Many of these compounds have allelopathic activity. On the other hand, sesquiterpene lactones and diterpene compounds have strong insect antifeedant, antifungal and allelopathic activities. Additionally, the essential oil (rich in α-pinene) has antifungal properties. All these biological activities suggest that Helianthus annuus has great potential for natural crop protection. Since the main sunflower crop residue is the flower head, we have revised the plant-protection properties of flowerhead components to highlight the potential valorization of that residue for the production of biopesticides.