1. capsaicin

3. Scoville heat unitsExamples 15,000,000– 16,000,000 Pure capsaicin [9]capsaicin [9] 8,600,000–9,100,000 Various capsaicinoids (e.g., homocapsaicin, homodihydrocapsaicin, nordihydrocapsaicin)homocapsaicinhomodihydrocapsaicinnordihydrocapsaicin 5,000,000–5,300,000Law enforcement grade pepper spray, [10] FN 303 irritant ammunitionpepper spray [10]FN 303 855,000–1,463,700 Infinity ChilliInfinity Chilli, [11] Naga Viper pepper, [12] Naga Jolokia pepper (ghost chili) [13][14] Trinidad Scorpion Butch T pepper [15] [11]Naga Viper pepper [12]Naga Jolokia pepper (ghost chili) [13][14]Trinidad Scorpion Butch T pepper [15] 350,000–580,000Red Savina habanero [16] 100,000–350,000 Habanero chiliHabanero chili, [17] Scotch bonnet pepper, [17] Datil pepper, Rocoto, Piri piri (African bird's eye), Madame Jeanette, Jamaican hot pepper [18] [17]Scotch bonnet pepper [17]Datil pepperRocotoPiri piri (African bird's eye)Madame Jeanette [18] 50,000–100,000 Byadgi chilliByadgi chilli, Bird's eye chili, [19] Malagueta pepper, [19] Chiltepin pepper, Pequin pepper [19]Bird's eye chili [19]Malagueta pepper [19]Chiltepin pepperPequin pepper [19] 30,000–50,000 Guntur chilliGuntur chilli, Cayenne pepper, Ají pepper, [17] Tabasco pepper, Cumari pepper (Capsicum Chinese)Cayenne pepperAjí pepper [17]Tabasco pepper 10,000–23,000Serrano pepperSerrano pepper, Peter pepper, Aleppo pepper, Cheong-Yang pepperPeter pepperAleppo pepperCheong-Yang pepper 2,500–8,000 Jalapeño pepperJalapeño pepper, Guajillo pepper, New Mexican varieties of Anaheim pepper, [20] Paprika (Hungarian wax pepper), Tabasco sauceGuajilloNew MexicanAnaheim pepper [20]PaprikaTabasco sauce 500–2,500Anaheim pepperAnaheim pepper, Poblano pepper, Rocotillo pepper, Peppadew, Padron pepperPoblano pepperRocotillo pepperPeppadewPadron pepper 100–500PimentoPimento, Peperoncini, Banana pepperPeperonciniBanana pepper 0No significant heat, Bell pepper, Cubanelle, Aji dulceBell pepperCubanelleAji dulce

4. TRPV1 cation channel protein PNAS, 2008, 105(21), 7451

5. Science, 2012, 336(6078), 220

6. Nature 2007, 449, 545 & 607