Cytotoxic and Anti-Inflammatory Effects of Ent-Kaurane Derivatives Isolated from the Alpine Plant Sideritis hyssopifolia

HPTLC Fingerprint Authentication of Selected Sideritis spp. Using a Pharmacognostic Approach

The genus Sideritis (Lamiaceae) comprises around 150 species, of which many are popular herbal remedies in Mediterranean folk medicine. Already mentioned by Dioscorides and Theophrastus, the "ironwort" or "Greek mountain tea" has been receiving increased attention in recent years. A European Union herbal monograph and assessment report (HMPC) has been issued, covering the species Sideritis scardica, S. clandestina, S. raeseri, and S. syriaca. This study presents results of a first pharmacognostic examination of the botanical and phytochemical differences among and between these emerging commercial species, and other, less studied species. An HPTLC method is proposed for normal phase separation of the species; this means applying two mobile phases on silica plates and subsequent derivatization with natural product reagent (NP/PEG) for visualization of phenolic compounds and anisaldehyde for a broader detection. With the help of selected reference compounds, a system suitability test was established for proper chromatographic separation. The method was applied to specimens from botanical gardens and commercial raw material in order to test its suitability for differentiation and authentication. The HPTLC analysis also includes, for the first time, S. hyssopifolia and other less used Sideritis species. The results might enable the development of a validated phytochemical fingerprint authentication procedure for quality assurance of Sideritis herba.

1-O-Acetylgeopyxin A, a derivative of a fungal metabolite, blocks tetrodotoxin-sensitive voltage-gated sodium, calcium channels and neuronal excitability which correlates with inhibition of neuropathic pain

Chronic pain can be the result of an underlying disease or condition, medical treatment, inflammation, or injury. The number of persons experiencing this type of pain is substantial, affecting upwards of 50 million adults in the United States. Pharmacotherapy of most of the severe chronic pain patients includes drugs such as gabapentinoids, re-uptake blockers and opioids. Unfortunately, gabapentinoids are not effective in up to two-thirds of this population and although opioids can be initially effective, their long-term use is associated with multiple side effects. Therefore, there is a great need to develop novel non-opioid alternative therapies to relieve chronic pain. For this purpose, we screened a small library of natural products and their derivatives in the search for pharmacological inhibitors of voltage-gated calcium and sodium channels, which are outstanding molecular targets due to their important roles in nociceptive pathways. We discovered that the acetylated derivative of the ent-kaurane diterpenoid, geopyxin A, 1-O-acetylgeopyxin A, blocks voltage-gated calcium and tetrodotoxin-sensitive voltage-gated sodium channels but not tetrodotoxin-resistant sodium channels in dorsal root ganglion (DRG) neurons. Consistent with inhibition of voltage-gated sodium and calcium channels, 1-O-acetylgeopyxin A reduced reduce action potential firing frequency and increased firing threshold (rheobase) in DRG neurons. Finally, we identified the potential of 1-O-acetylgeopyxin A to reverse mechanical allodynia in a preclinical rat model of HIV-induced sensory neuropathy. Dual targeting of both sodium and calcium channels may permit block of nociceptor excitability and of release of pro-nociceptive transmitters. Future studies will harness the core structure of geopyxins for the generation of antinociceptive drugs.