Mark Christensen

Apples are a commonly consumed fruit linked with reducing the risk of several chronic diseases, including cancer. Some of the health benefits of apples are related to their secondary metabolites, known as phytochemicals. The type of phytochemicals and their distribution differ within the various parts of an apple (skin vs. flesh) and are affected by cultivar type and food processing methods. Several studies have reported higher content of apple phytochemicals in the skin compared to the flesh, but the skin only makes up 10% of the weight of the apple. Only a few studies have reported on differences in the phytochemical content relative to the weight of the skin compared to the whole apple. In this comparative study, we used liquid chromatography–mass spectrometry (UPLC-QTOF-MSLC-MS) to identified phenolics (flavonoids and phenolic acids) and triterpenoids as the main phytochemicals in the skin and flesh of a New Zealand (NZ) heritage apple cultivar known as ‘Monty’s Surprise’. We further evaluate the effect of two simple household processing techniques, puree and air dehydration, on phytochemical concentration. Our preliminary analysis showed that ‘Monty’s Surprise’ contained a higher concentration of catechin, epicatechin, total procyanidins and chlorogenic acid when compared to the commercial apple cultivars ‘Red Delicious’ and ‘Braeburn’. Furthermore, flavonols (quercetin glycosides) were present mainly in the skin, whereas chlorogenic acid levels were higher in the flesh. Moreover, our data showed that apple puree retains a phytochemical concentration similar to that of fresh apple, whereas air dehydration appears to be more destructive to apple phytochemicals. The findings from this study point out that, to obtain the greatest health benefits from apples, it is important to consume the whole apple, including skin. Additionally, an apple’s health effects vary in relation to the phytochemical profile of the apple that is consumed. Furthermore, this study identifies a simple household processing method for long-term storage that preserves the apple’s phytochemical profile to achieve maximum health benefits.

Cancer is one of the leading causes of death globally. Epidemiological studies have strongly linked a diet high in fruits to a lower incidence of cancer. Furthermore, extensive research shows that secondary plant metabolites known as phytochemicals, which are commonly found in fruits, have onco-preventive and chemo-protective effects. Apple is a commonly consumed fruit worldwide that is available all year round and is a rich source of phytochemicals. In this review, we summarize the association of apple consumption with cancer incidence based on findings from epidemiological and cohort studies. We further provide a comprehensive review of the main phytochemical patterns observed in apples and their bioavailability after consumption. Finally, we report on the latest findings from in vitro and in vivo studies highlighting some of the key molecular mechanisms targeted by apple phytochemicals in relation to inhibiting multiple ‘hallmarks of cancer’ that are important in the progression of cancer.