Capsaicin structure

Camphor, molecular model of, 129 specific rotation of, 296 Cannizzaro, Stanislao, 724 Cannizzaro reaction. 724 mechanism of, 724 Caprolactam, nylon 6 from, 1213 Capsaicin, structure of. 78 -curbahlehyde, aldehyde name ending, 696... 

These compounds are responsible for the hotness in chillis (hot peppers), the degree of pungency being related to the length of the acid side chain. Total capsaicinoid content is around 1 % of the dried fruit, the majority of which is usually capsaicin. Structurally, capsaicinoids are vanillyl-acyl amide analogues (Tucker and Debaggio 2000). 

The spicy flavor of cayenne pepper is due mainly to a substance called capsaicin. The following sequence of steps was used in a synthesis of capsaicin. See if you can deduce the structure of capsaicin on the basis of this synthesis. 

Capsaicin, also known as N-Vanillyl-8-methyl-6-(E)-noneamide, is the most pungent of the group of compounds called capsaicinoids It is a common ingredient in varieties of pepper such as habanero, Thai, tabasco, cayenne etc. One target with which capsaicin interacts is the capsaicin receptor, an ion channel belonging to the superfamily of TRP channels. Because of the structural relation to other TRP channels and because the vanilloid moiety is an essential component of capsaicin, the capsaicin receptor is also called TRPVI or vanilloid receptor (VR1). It is involved in heat and pain perception. 

TRPV1 is a nonselective cation channel predominantly expressed in sensory neurons and activated by capsaicin, heat (>42°C), pH (<5.4), and noxious stimuli. Several compounds have advanced into clinical development and have been extensively covered in recent reviews [5,34—39]. Among these, MK-2295 (structure not disclosed), AMG 517 (38), SB-705498 (39), and GRC-6211 (structure not disclosed) have reportedly encountered safety issues [35]. In phase II clinical trials with MK-2295, patients experienced an increase in core body temperature... 

Now, to return to the orange stain, formed on the surface of a pan by adsorption of capsaicin from a solution (the curry). Such organic dyes are usually unsaturated (see the structure I above), and often comprise an aromatic moiety. The capsaicin, therefore, has a high electron density on its surface. During the formation of the adsorption bond, it is common for this electron cloud to interact with atoms of metal on the surface of the pan. Electron density flows from the dye molecule via the surface atoms to the conduction band of the bulk metal. The arrows on Figure 10.4 represent the direction of flow as electron density moves from the charge centroid of the dye, through the surface atoms on the substrate, and thence into the bulk of the conductive substrate. 

Capsaicin was extracted and named by Thomas Thresh in 1846, and its chemical structure was determined in 1919. The Scoville Unit was also developed in 1912 as a measurement of the hotness of chili peppers (Scoville 1912). A pepper with 1000 Scoville Units means that an alcoholic extract must be diluted 1 1000 before it ceases to be hot. The Mexican habanero pepper has an astonishing 350,000 Scoville Units. 

The primary chemicals of interest in chilies are capsaicinoids, namely capsaicin (0.02%) and dihydrocapsaicin (figure 8.11). Also found are flavonoids, carotenoids (capsanthin), steroid saponins (capsicidin), and ascorbic acid or vitamin C (0.2%). Capsaicin has a vanilloid chemical structure. Mechanisms of Action... 

Suzuki T, Fujiwake H, Iwai K (1980) Intracellular localization of capsaicin and its analogues, capsaicinoid, in Capsicum fruit. 1. Microscopic investigation of the structure of the placenta of Capsicum annuum var. annuum cv. Karayatsubusa. Plant Cell Physiol 21 839-853 Ohta Y (1963) Physiological and genetical studies on the pungency of Capsicum IV. Secretory organ, receptacles and distribution of capsaicin in the Capsicum fruits. Jap J Breed 12 179-183... 

Mason, J. R., Bean, N. J. Shah, P. S., and Clark, L. (1991). Taxon-specific differences in responsiveness to capsaicin and several analogues correlates between chemical structure and behavioral aversiveness. Journal of Chemical Ecology 17, 2539-2552. 

Solanaceae), acts as competitive inhibitor for ubiquinone in Complex I. Methyl capsaicin is more potent than capsaicin, indicating that the phenolic OH is not essential for the activity [297]. Other natural inhibitors of Complex I are annonaceous acetogenins. These compounds belong to a wide group of natural products isolated from several species of the Annonaceae family, which include more than 250 molecules with diverse chemical structures. Among the various classes, it seems that monotetrahydrofuranic derivatives are less potent than other acetogenins [296, 299]. 

Figure 12.6 Structures of capsaicin, maple lactone, and methyl anthranilate.

Scheme 1 Chemical structures of natural vanilloid receptor agonists a, capsaicin, the irritant principle in hot peppers b, resiniferatoxin (RTX), isolated from the cactuslike plant Euphorbia resinifera c, the triprenyl phenol scutigeral, found in an edible, non-pungent mushroom d, the sesquiterpenoid dialdehyde isovelleral, found in pungent mushrooms.

Figure 30-29 Structures of the active components of cannabis, tetrahydrocannabinol, and cannabidiol, and structures of endogenous cannabinoids and of the vanilloid lipid capsaicin.

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