Research development of Salacca zalacca skin against metabolic syndrome: A Review

Metabolic syndrome (MetS) is a group of metabolic disorders involving obesity, insulin resistance, dyslipidaemia and hypertension. The pathogenesis of MetS includes contributing factors such as genetics and epigenetics, physical inactivity, pollutant exposure, and high fat-high sugar intake that develop into a variety of interrelated pathomechanisms. There are various approaches to managing the MetS, including development of herbal medicine which is currently trending. One of the potential herbal products is Salacca zalacca (SZ) skin. Salak is a native Indonesian fruit that is also grown in the Asia Pacific region, such as Malaysia, Thailand, the Philippines, and others. However, the management of SZ skin is still limited. Thus, we reviewed studies on SZ skin related to MetS. In this review, we found that SZ skin of various cultivars contain saponins, flavonoids, triterpenoids, steroids, and phenols, which are sources of antioxidants. Moreover, an in vitro study found that SZ skin extract inhibits the activity of α-glucosidase enzyme, a key glucose breakdown enzyme that plays a role in the development of hyperglycaemia. In vivo studies also observed that SZ skin extract at a dose of 0.4 mg/mL can increase the expression of SIRT-1, BDNF, and SOD in zebrafish exposed to 3% glucose. In alloxan-induced diabetic rat model showed that the administration of SZ skin extract can reduce blood glucose levels. However, studies on SZ skin as anti-hypertensive and anti-hypercholesterol are very limited. Further studies are needed to consider SZ skin as a potential herbal medicine candidate, especially in managing MetS.