1) When mixed together in aqueous solutions (since both are water-soluble vitamins), they form a 1:1 complex that turns the solution yellow, rendering both compounds useless. This complexation may be the result of a donor-acceptor interaction between L-ascorbic acid (donor) andniacinamide (acceptor), which may be similar to the interaction that occurs between tryptophan and niacinamide.=>互相銷功效
2) In the presence of UV light, niacinamide andL-ascorbic acid can form hydrogen peroxide, a known pro-oxidative compound. => UV下會產生H2O2 (過氧化氫/雙氧水),係強氧化物。