Modulation of UVB-induced oxidative stress and inflammation in skin keratinocytes (HaCaT) utilising unfermented rooibos and honeybush aqueous extracts

•UVB radiation triggers diverse biological responses, contributing to the onset of skin cancer.•Tea polyphenols protect against UVB-induced damage by modulating oxidative stress and inflammation.•South African rooibos and honeybush teas exhibit anti-inflammatory properties targeting early cancer stages.•Honeybush reduces UVB-induced IL-1α, maintains cell viability, and uniquely decreases IL-6 secretion. Exposure to Ultraviolet B (UVB) radiation can trigger a diverse array of biological responses that have the potential to contribute to the onset of skin cancer. Natural compounds, such as tea polyphenols, have been shown to protect against UVB-induced damage by modulating oxidative stress, inflammatory response, and cell proliferation. The chemopreventive and anti-inflammatory properties of South African rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) herbal teas have been shown to mainly target the early stages of cancer development through mechanisms that involve intracellular interleukin-1α (IL-1α) inhibition. Thus, the aim was to investigate the preventive effects of unfermented rooibos and honeybush aqueous extracts against UVB-induced oxidative stress and inflammation in HaCaTs. Honeybush was found to reduce the accumulation of UVB-induced IL-1α while maintaining cell viability and without affecting apoptosis. Furthermore, only honeybush extract was able to decrease the secretion of interleukin-6 (IL-6) caused by UVB exposure. Honeybush and rooibos extracts significantly decreased the secretion of UVB-induced interleukin-8 (IL-8). Except for rooibos extract at a concentration of 0.2 mg/mL, both extracts restored the expression of antioxidant genes to levels observed prior to UVB exposure. The anti-inflammatory effects of these herbal tea extracts are likely attributed to the antioxidant properties of their polyphenolic constituents, which modulate the oxidative stress-induced pathways governing inflammatory responses. Exposure to UVB radiation poses a risk for skin cancer development, but natural compounds like tea polyphenols offer protective benefits by regulating oxidative stress, inflammation, and cell proliferation. This study explored the preventive effects of unfermented rooibos and honeybush extracts against UVB-induced oxidative stress and inflammation in HaCaTs. Honeybush extract notably reduced UVB-induced IL-1α accumulation without compromising cell viability or apoptosis, and it also decreased UVB-induced IL-6 secretion. Both