Plants are considered the potential resources of various bioactive compounds. A number of medicinal plants have been widely used as functional foods and alternative medicines for the prevention and treatment of several diseases.
Mulberry is a well-known medicinal plant. Mulberry leaves contain numerous chemical constituents. 1-Deoxynojirimycin (DNJ), phenolics and flavonoids are the prominent functional compounds.
Scientific studies suggest that mulberry leaves contain a cluster of bioactive compounds and possess several pharmacological effects.
DNJ is regarded as the most potent antihyperglycaemic compound of mulberry leaves. As DNJ and glucose have similar structures, DNJ competitively blocks the active site of polysaccharide-degrading enzymes in the digestive tract. When the enzymes are inhibited, digestion and absorption of dietary carbohydrates are eventually diminished.
DNJ, phenolics and flavonoids were associated with lipid-lowering effects of mulberry leaves through multiple mechanisms of action. The extract of mulberry leaves enriched with DNJ, quercetin and kaempferol activated the expressions of AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR)-α, leading to the increase in β-oxidation of free fatty acid and lipid breakdown.
Mulberry leaves suppressed body weight gain induced by chronic ingestion of high-fat diet. It was hypothesized that phenolics were responsible for anti-obesity effect of mulberry leaves.
Mulberry leaves reduced blood pressure and heart rate by inhibiting angiotensin-converting enzyme.An investigation of vascular reactivity revealed that mulberry leaves improved the responses of blood vessels to exogenous stimulators. The impaired reactivity of blood vessels, including diminished dilatation and increased constriction, were significantly restored to the normal levels after long-term treatment of mulberry leaves.
Phenolics and flavonoids were found to be excellent antioxidants. The fractions of mulberry leaves extract containing the higher values of phenolic and flavonoid compounds exhibited the stronger antioxidative property.