natural-products-in-plant-pest-management

Natural Products from Plants 57of certain seedlings and shows potential as an herbicide. Scopoletin has astimulating effect on seed germination but an inhibiting effect on seedlinggrowth, indicating a potential as pre-emergence herbicide.Flavonoids are the largest group of natural phenolic compounds foundin plants. More than 5000 different flavonoids have been described. All flavonoidshave one thing in common, namely a 15-carbon ‘skeleton’ structuredin three phenyl rings (A, B and C; Fig. 3.21). Other examples are shownin Fig. 3.22.A large variety of biological activities have been associated with flavonoids,including antiviral, anti-inflammatory, antioxidant, antidiabetic,anticancer, insect-repelling and free-radical-scavenging activities. Whatmakes this group extraordinary from an industrial perspective are the excessivequantities found in both edible and non-edible plants as well as theirpotential to be developed into natural products. It is estimated that about 2%of all carbon photosynthesized by plants is converted to flavonoids and thisamounts to approximately 1 × 10 9 tons per annum. With this enormousamount of flavonoids available, and in light of the numerous bioactivitiesidentified to date, the time is now ripe to consolidate our knowledge of theBACFig. 3.21. Typical fl avonoid structure.HOOHOHOHOHOHOOHOOOHOHOHOHOHOHOHEpicatechin Gallocatechin (+)-CatechinOHOHOHOHOHOHHOOHHOOHOOHOHyperosidegalactoseOOHOQuercitrinrhamnoseFig. 3.22. Flavonoid examples.