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Grayanotoxins
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Grayanotoxins are toxic diterpenes with polyhydroxylated cyclic hydrocarbon structures that do not contain nitrogen (Figure 102.1). These compounds are previously known as rhodotoxin, andromedotoxin, or acetylandremodol. GTXs are nonvolatile and heat-stable compounds and are readily soluble in both water and lipids.12 There are more than 25 isoforms of grayanotoxins isolated from Rhododendron plants. Grayanotoxin I (GTX I) and Grayanotoxin III (GTX III) are the most abundant grayanotoxins found in rhododendron. Grayanotoxin II (GTX-II) is also found in much lower amounts.12
Nature and applications of scorpion venom: an overview
Published in Toxin Reviews, 2020
Saadia Tobassum, Hafiz Muhammad Tahir, Muhammad Arshad, Muhammad Tariq Zahid, Shaukat Ali, Muhammad Mohsin Ahsan
Toxins interact with VGSCs in two ways. It either results in a blockage of pore when the neurotoxin physically obstructs the pore and inhibits the conductance of sodium ions, or in a modification of the gating, that altered the voltage-dependence and gating kinetics of the ion channels. Toxins that interact with the site 1 use first mechanism. For example, tetrodotoxin (TTX) and sexitoxin (STX) are pore blockers of site 1. Grayanotoxin and batrachotoxin are site 2 toxins which prevent inactivation and therefore, channel remain persistently active (Stevens et al. 2011). Scorpion α-toxins and sea anemone toxins bind to site 3 and inhibit the inactivation (Possani et al. 2000). Scorpion β-toxins and spider β-toxins are site 4 toxins which shift the activation toward hyperpolarized state (Shichor et al. 2002). Site 5 toxins like ciguatoxins and brevetoxins display a real effect upon binding with VGSC, for example, inhibition of activation and the hyperpolarizing shift of voltage-dependence activation. Finally, δ-conotoxins interact with site 6 and produce similar outcomes as the site 3 neurotoxins by inhibiting inactivation (Figure 3) (Stevens et al. 2011).
Cell signal transduction: hormones, neurotransmitters and therapeutic drugs relate to purine nucleotide structure
Published in Journal of Receptors and Signal Transduction, 2018
Grayanotoxin [15] and NCGG [22] are, respectively, openers of voltage-gated Na+ channels and ligand-gated ENaCs. In contrast to the channel openers, voltage-gated [16–19] and ligand-gated antagonists [20,21] target the imidazole moiety of the guanine ring and region to the left of fitting points N7C8N9. cGMP is effective in decreasing cellular Na+ uptake and relieving extracellular sodium self-inhibition at the ENaC receptor [40,41]. Template 23 demonstrates similarity, in respect of molecular size and relative structure, for aldosterone and cGMP. Aldosterone inhibits the production of NO and cGMP; suppression of aldosterone production relieves renal oxidative stress in rat diabetic kidney [42]. Templates 24–26 provide evidence of relative molecular similarity within the disparate structures of tetracaine, trans-retinol and l-cis-diltiazem, which possess a common blocking property on CNG channels [5,43]. Comparative fitting values for the ligand structures given in Figures 5 and 6 are very similar at 0.06 ± 0.03 Å–0.07 ± 0.04 Å.