**3.2 Biosynthesis of pinocembrin**

In plant propolis, pinocembrin is one of the most abundant flavonoid, and it could also be commonly found in a most plants. Biological synthesis plays a significant part in synthesizing pinocembrin owing to its increased yield and low cost in production. They can extract pinocembrin from product of nature but that methodology is of high production cost and reduced yield. Biological synthesis from microorganisms features the advantages of low cost and large product yield, which compensate for the lack pinocembrin natural sources [47]. *Escherichia coli* has been known to be used in the production of pinocembrin. Recently, efficient way of producing pinocembrin has been the main goal of most researchers. Biological production of pinocembrin mostly requires that one needs to supplement an expensive phenylpropanoid starting materials, resenting a key problem in previous studies. Genetic engineering is now the breakthrough in the synthesis of pinocembrin biosynthesis, where there is the usage of bacteria to construct the synthesis of pinocembrin from glucose. To manufacture the flavonoid precursor (2S)-pinocembrin directly from glucose, four-vectors have been assembled, 3-deoxy-D-arabinoheptulosonate-7-phosphate synthase, chorismite mutase/pre-phenate dehydratase, phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4CL), chalcone synthase (CHS), chalcone isomerase (CHI), malonate synthetase, malonate dehydratase, and malonate carrier protein. Pinocembrin synthesis from glucose can be achieved through adjustment of other corresponding parameters in the synthetic pathways [47].
