[2][3] The highest amount of vanillic acid in plants known so far is found in the root of Angelica sinensis,[4] an herb indigenous to China, which is used in traditional Chinese medicine.
[5] It is one of the main natural phenols in argan oil.
[citation needed] It is also found in wine and vinegar.
[6] Vanillic acid is one of the main catechins metabolites found in humans after consumption of green tea infusions.
With Pd/C, NaBH4, and KOH as the oxidizing agent, the conversion was reported to occur in ~89% yield.