Rooibos tea extracts inhibit osteoclast formation and activity through the attenuation of NF-κB activity in RAW264.7 murine macrophages

Abstract

Rooibos tea is a naturally sweet and aromatic tea that is native to the Western Cape province of South Africa. Rooibos is usually fermented to produce the traditional reddish brown colour and has been found to have numerous health benefits. These include beneficial effects on osteoblasts; however, its effects on osteoclast formation and activity are unknown. Osteoclasts are large, multinucleated cells responsible for bone resorption. Binding of RANKL to its receptor on osteoclast precursors triggers the NF-κB signalling pathway leading to the formation of osteoclasts. Certain bone destructive diseases, such as osteoporosis, are characterised by overactive osteoclasts. The inhibition of osteoclasts may offer a potential mode to prevent these diseases. The polyphenol contents of both fermented and unfermented tea extracts were similar although the radical scavenging activity of fermented rooibos tea was lower. Both tea extracts were not cytotoxic and inhibited osteoclast formation. Fermented rooibos tea extract caused a greater reduction in osteoclast resorption and the associated gene expression when compared with unfermented rooibos tea. Both tea extracts were shown to attenuate NF-κB activity. Fermented rooibos was found to have a more potent inhibitory effect on osteoclasts than unfermented rooibos extract and therefore may have a beneficial effect on bone health.

Study assessing the efficacy of herbal teas on bone health and quality of life in a population with osteopenia: rooibos actions on melatonin and tulsi actions on quality of life.

“…Specifically, rooibos consumption significantly decreased CTX levels compared to placebo (coriander) consistent with past studies demonstrating a rooibos-mediated inhibitory action on osteoclast activity through attenuation of NF-κB activity (39)(40)(41). Osteoclastogenesis leads to large, multinucleated cells following binding of RANKL to RANK on preosteoclasts triggering the NF-κB signaling pathway (40) and so an inhibition of osteoclast activity through daily consumption of rooibos tea may offer a safe intervention to prevent bone loss (39)(40)(41). The osteoclast-inhibiting actions of rooibos tea may be attributed to aspalathin, one of its chemical constituents, which has demonstrated osteoclast-inhibiting activity in vitro (39).…”

Isorhamnetin attenuates osteoarthritis by inhibiting osteoclastogenesis and protecting chondrocytes through modulating reactive oxygen species homeostasis

“…However, phosphorylation of ERK, JNK and p38 considerably decreased after Iso treatment. RANKL‐induced NF‐κB activation is essential for initiating osteoclast differentiation . As indicated in Figure , western blotting analysis showed that RANKL treatment drastically caused degradation of IκBα while increasing phosphorylation of p65.…”

Red Rooibos Tea Stimulates Osteoblast Mineralization in a Dose-Dependent Manner

“…More specifically, orientin significantly increased mineralization at concentrations of 0.1-1 µM as well as 15-100 µM; while luteolin significantly increased mineralization at 5 µM. Extracts from both red and green rooibos tea have demonstrated the ability to inhibit the formation of osteoclasts as well as their activity in a rodent cell model suggesting potential health benefits in bone [36]. Furthermore, it was demonstrated that RR tea extracts inhibited osteoclast formation and activity in a dose-dependent manner and were more potent than green rooibos tea extracts.…”