The asymptotics of optical activity n₊-n_- at ω≫ Ry are ω^-5 for oriented chiral molecules and crystals, and ω^-7 for isotropic media of chiral molecules and polycrystals. However, with a further increase of ω both fall-offs change to ω^-3 due to spin-orbit interaction. The expectation value in the numerator of the last asymptotics practically coincides, up to an overall factor, with that of the weak interaction responsible for the P-odd energy difference of right- and left-handed molecules.