12.6.3Geraniol

Geraniol, farnesol and geranylgeraniol are another class of PPARg agonists that stimulate PPARg.45 The geraniols (Figure 12.12) are found in rose oil, palmarosa oil, citronella oil and in geranium, lemon and other essential oils. Geraniols have been documented to inhibit LPS-induced stimulation of COX-2, iNOS and NF-kB in mM concentrations.46 However, bioavailability data are unavailable for geraniol at this time.

12.7 Agonists of LXR that Reciprocally Inhibit NF-jB

Many of the natural product agonists of LXR resemble cholesterol-like molecules such as plant sterols. Many cholesterol intermediates are also agonists for LXR. The following are a few examples of common natural product LXR agonists. However, there are few human bioavailability data available.

12.7.1Stigmasterol

Stigmasterol is a plant-derived sterol and a potent agonist of LXR (Figure 12.13). It is found in lipid-rich areas of plants or oils of soybean, calabar bean, rape seed and Chinese herbs such as ginseng. The addition of stigmasterol to CHO-7 cells was able to increase expression of many genes downstream of LXR, such as the ATP binding cassette transporter (ABCA1), which promotes the e ux of cholesterol.47

Stigmasterol is also known for its anti-inflammatory activity.48 In osteoarthritis cell culture models stimulated by IL-1, stigmasterol in a 20 mg/ml concentration was able to inhibit NF-kB-induced expression of IL-6 and MMP-3.

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Figure 12.12 Geraniol.

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Figure 12.13 Stigmasterol.