Polyphenolic antioxidant profiles of yellow camellia.

Yellow camellia (section Nitidissima Chang) is a subgroup of tea plant with golden yellow flowers. It is a very rare species with potential as antioxidant rich plant as it is closely related to tea. We found, for the first time, that the antioxidant capacity and polyphenolic constituents of six yellow camellia species varied widely. Among them, the dry leaf of Camellia impressinervis had the highest level of oxygen radical absorbance capacity (ORAC, 2270.9μmolTE/g), total phenolic content (TPC, 475.6μmolGAE/g), and proanthocyanidin content (PAC, 66.1μmolCE/g). The ORAC level correlated well with TPC (R2=0.9402), and PAC (R2=0.9954). The compounds responsible for antioxidant activities were further profiled by HPLC and LC-MS analysis. Compared to the commonly consumed tea leaves, yellow camellia leaves contain more diverse phenolic compounds, including ellagitannins, proanthocyanidins, taxifolin deoxyhexose, apigenin derivatives, kaempferol derivative, quercetin derivatives, glucosyl isorhamnetin, (epi)catechin-(epi)afezelechin polymers and platphyllosides. Unlike tea leaves, no caffeine is detected in the yellow camellia leaves. The antioxidant activity of the polyphenolic compounds were further verified by precolumn treatment of the extracts with a stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH).