Two distinct actions of the chamomile flavonoid
Apigenin is a flavonoid found in chamomile, parsley, and celery. It is studied for binding the benzodiazepine site on the GABA-A receptor, the same broad site targeted by anti-anxiety drugs, which is the proposed basis for its mild calming and sleep-supporting reputation, though its affinity is weak. Separately, apigenin can inhibit CD38, an enzyme that consumes NAD+, which is the rationale behind its inclusion in some longevity-oriented formulas aiming to preserve cellular NAD+.
These are two unrelated mechanisms that explain its appearance in both sleep and NAD+ products.
How firm the human evidence is
Most of the GABA and CD38 findings come from cell and animal studies, and chamomile's traditional calming use is suggestive rather than proof of a specific apigenin dose effect. Bioavailability of oral apigenin is also limited. The mechanisms are plausible but the clinical evidence in people is preliminary.
This is general educational information, not medical advice. Apigenin may interact with sedatives and other medications. Consult a qualified professional before use.