Eriocitrin is one of those compounds you've probably never heard of by name, even though you've eaten plenty of it. It's the main flavonoid polyphenol in lemons, concentrated in the peel and to a lesser extent the juice. The scientific community has been studying it for decades, particularly Japanese researchers who started looking at it seriously in the 1990s.
Most people associate lemons with Vitamin C, and Vitamin C is genuinely useful. But it's not the most interesting compound in a lemon from a research angle. Eriocitrin and its sister compound hesperidin are the polyphenols doing much of the heavy lifting that traditional Mediterranean diets get credit for.
The research on eriocitrin has two main strands. The first is antioxidant activity, where eriocitrin and its breakdown products show strong free radical neutralisation in lab assays. The second is metabolic effects, particularly around lipid metabolism. Animal and early clinical studies have shown eriocitrin can affect triglyceride levels and aspects of glucose metabolism, though the evidence is still emerging.
For a metabolic supplement, eriocitrin makes sense as a complementary ingredient. It works through different pathways than saffron (which is mood and satiety focused) and blood orange anthocyanins (which are vascular and antioxidant focused). Three botanicals, three different mechanisms, one gummy.