Complex sentence: UDP-glucuronic acid also serves as the source of glucuronic acid for the biosynthesis of polysaccharides and is an intermediate in the biosynthesis of ascorbic acid (except in primates and guinea pigs).
Split into simpler sentences: UDP-glucuronic acid serves as the source of glucuronic acid for the biosynthesis of polysaccharides. It is also an intermediate in the biosynthesis of ascorbic acid (except in primates and guinea pigs).