Anti-inflammatory and Anti-cancer Effects of Kawakawa (Macropiper excelsum) Leaves

Abstract

Kawakawa leaves have a well-established history of being used as a restorative of human health, specifically among New Zealand’s Māori population. The early Māori had healthier bodies with fewer risks of serious diseases, including cancers. This is potentially linked to the frequent consumption of medicinal plants. Kawakawa leaves are considered to have numerous health advantages in terms of treating an array of ailments, including colds, diarrhoea, skin problems and so forth. Regardless, scientific enquiry into the basis of such benefits has been lacking. Kawakawa is a member of the varied pepper family, which includes the black pepper. Peppers play a significant role in food and medicine globally. The therapeutic effects of numerous peppers’ leaves, including antioxidant, anti-inflammatory and anticancer properties, have been evidenced in various studies. Nevertheless, the medicinal properties of kawakawa leaves remain less understood. The antioxidant property of kawakawa leaves was determined through analysing the activity to scavenge DPPH, ABTS and NO radicals. Furthermore, appropriate solvents for extracting kawakawa leaves were selected via a comparison of antioxidant activity. The results indicated that kawakawa leaf extracts possess an antioxidant capability in terms of diminishing DPPH, ABTS or NO radicals, however, activities to scavenge those free radicals are varied. Additional investigation was undertaken using in vitro models, as a means of analysing the antiinflammatory properties of kawakawa leaf extracts. In HEK-Blue 2 and HEK-Blue 4, NOD2 WT and NOD2 G908R cells, kawakawa leaves were found to have an antiinflammatory effect through inhibiting the secreted alkaline phosphatase (SEAP) production. Subsequently, the kawakawa leaf extract concentration required for inhibiting 50% of SEAP was determined for gene expression experiments. Further, HT 29 cell lines were adopted for determining the kawakawa leaves’ anti-cancer effects. The concentration of kawakawa leaves required in order to destroy 50% of HT 29 cells was calculated for further gene expression analysis. Finally, three target genes, namely IL6, IL10 and NFKB1, were analysed through realtime PCR. The kawakawa leaf extract was able to down-regulate the IL6 and NFKB1 genes. This project’s findings provide evidence that kawakawa leaves have antioxidant, antiinflammatory and anti-cancer effects. Future research should seek to determine the bioactive ingredients of kawakawa leaves. Moreover, varied cell models and associated gene expression is warranted. Of further benefit would be animal research and clinical experimentation, with the objective of analysing kawakawa leaves beneficial health effects in vivo.