Overview of potential individual phenolic compounds of African walnut extracts and cytotoxicity assessment in lung cancer cell line (A549)

African Walnut extracts are often mixed in decoctions for management of diseases (e.g. cancer) in ethnobotanical medicine. There is no report detailing the group of individual polyphenols, contained in the nut, which may be influencing the health status of persons consuming the herbal mixtures. There are also no specifications on the types of cancer the extract mixtures are applied on. This raises questions as to whether the extracts administered have direct chemotherapeutic effects or simply act as a nutritional supplement to boost the immune system of patients. This study profiled and compared the total and potential individual polyphenols of boiled, roasted, and unprocessed nuts, and assessed the cytotoxicity of their sequential extracts in A549 (lung cancer) cell line. Individual polyphenols, resolved and compared with external standards at 280, 332 and 355 nm, using high performance liquid chromatography (HPLC), showed that African walnut contains compounds mainly from flavan-3-ol, phenolic acid, and flavanol groups. The Folin-Ciocalteau assay, quantified as Gallic acid equivalent (GAE) per gram dried weight (DW) of samples, revealed higher levels of total polyphenols in unprocessed nuts (20.79±1.00 mg GAE g‑1 DW), while boiling (9.90±1.80 mg GAE g‑1 FDW) and roasting (9.32±2.70 mg GAE g‑1 DW) reduced the concentrations by more than 50%. There were no significant cytotoxic effects of the extracts on A549 cell lines. These findings suggest that addition of African walnut extracts in decoctions for management of lung cancer act mainly as a nutritional supplement to boost the immune system of patients, rather than as a chemotherapeutic agent.