Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 “To me, life without veal stock, pork fat, sausage, organ meat, demi-glace, or even stinky cheese is a life not worth living.” “I’ve long believed that good food, good eating, is all about risk. Whether we're talking about unpasteurized Stilton, raw oysters or working for organized crime 'associates,' food, for me, has always been an adventure.” In 2020, over 200 million people in USA consumed HEINZ® ketchup, the total annual sale is over 20 billion dollars. It occupies over 60% of the entire ketchup market in USA. Natural Flavor? !Inorganic salts? !Peptides? Anthony Bourdain (1956-2018) !Steroids? !Glycogen? !Organic bases? !Fatty acid? O OH Theogallin Me Me HO OH Me H O NH O S N OH 2 H Me OMe O N Me HO N O OH H Me O Me Sucrose Capsaicin HO OHO (table sugar) OH Alitame Umami—savory > 2000 times sweeter Chili Pepper Is it a taste? O OH HO OH OH O O HO O O N H HO Succinic acid MeO Me H OH O H H HO N Cinchona Tree O OH isolated in 1820 O Quinine HO O OH aganist malaria Intensify saltiness Aldosterone Adipic acid Tartaric acid Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 Before 1910s, people generally believed that there were 4 types of basic tastes the O O combinations of which could lead to a variety of flavors in dishes. Those four basic are sweet, salty, bitter and sour. In 1907, Professor Ikeda from Tokyo Imperial University noticed Na+ HO O- that something in “dashi” made the dish extremely savory. One year later, he isolated a slightly brown crystal from “dashi” which he believed was the source of the savory taste and NH2 named it “Ajinomoto”—the essence of flavor. The discovery of monosodium glutamate is Monosodium glutamate also the discovery of the fifth basic taste—“umami”. (MSG) Chemical synthesis Extraction Fermentation ~ 2 million tons / year 1909-1962 1962-1973 currently O O CO, H2 O NH4CN NH2 NaOH, H2O NC HO O- oxo reaction NC H Strecker NC CN + Ajinomoto ~ 2 ¢/ml NH Na 2 Kikunae Ikeda (1864-1936) “essence of flavor” Taste signals are eventually received and processed in gustatory cortex. Type 2 Type 1 Type 3 (GPCRs) The primary organ for taste sensation— Salty Sweet, bitter and umami Sour oral cavity. Taste Mostly activated by Activated by a large variety of Mostly activated by receptor cells (TRCs) inorganic salts and adjust organic molecules ans use protonic acids and can are mainly located in ion concentrations intra- ATP as the signal transmitter. accumulate cations in taste buds. and extracellular. the cells. Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 Nowadays, it is generally accepted that there are two types of salty taste receptors: epithelial sodium channel (ENaC) and transient receptor potential cation channel subfamily V member 1 (TRPV1). ENaC is cation-specific and selectively sensitive to Na+ and Li+ however TRPV1 is cation-nonspecific and can respond to a wide variety of + 2+ + cations (K , Ca , NH4 …) and even organic molecules. Recommended daily NaCl intake is about 2.3 g O Me Me N H one piece of patty one slice of pizza Me ~ 1.0 g NaCl ~ 1.2 g NaCl Spilanthol Taste enhancers: compounds that have no or little intrinsic taste but can significantly intensify one or Me several of the five basic tastes upon ingested. Positive allosteric modulators (PAMs): compounds that can bind to spots other than orthosteric spots O and trigger similar downstream biological Me reactions. N O OH H OH O NH O Me Me O O Me HO Na+ Me Sanshool O- OMe H2N N N R Me N H Me O NH2 H H OH NH2 H2N OH then Me Sodium aspartate Arginyl dipeptides NGCC (IFF) Methyl lactate Me3NO, MeCN EDC, HOBt r.t. DCM, r.t. R1 CN NaHMDS, THF (OC) Fe 1, DIBAL (OC)3Fe R = Ph P+Br- 3 o 1 3 0 oC → r.t., 90% toluene, -20 C O Fe (CO) CN 2. (EtO)2POCH2CO2H 3 12 Fe(CO) toluene 3 Me r.t., 75% Me OH R CN Me CHO 2 reflux, 80% KHMDS, THF (OC) Fe 1, DIBAL O Me CHO 3 o (OC)3Fe 2,4-hexadienal -78 oC → r.t., 74% CN toluene, -20 C O OH O N N S 2. (EtO)2POCH2CO2H R2 = Me r.t., 70% N N Me Ph Tet. Lett. 2012, 6000; Chemical Senses 2019, 91 Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 OH HO Amberlite 15 L-alanine Br2, MeOH O H o BuOAc/H O NaOH, H2O CO2H H2O, 0 C → r.t. 2 HO HO N HO OH N HO CHO then Ni/H O OH O 2 Me OH J. Agric. Food Chem. 2003, 4040 Me CO2 Hexose Maillard reaction: see Food Chemistry (Baranlab GM by David Peters in 2019) Alapyridaine Stewed beef OH OH Preliminary SAR study HO HO N Me N OH N Me CO2 Me CO HO CO 2 N 2 inactive bitter OH OH O Me CO2 HO !both the hydroxyl and hydroxymethyl N N HO !the absolute configuration N O !the carboxylate group Me CO Me CO A general taste enhancer? 2 2 Mol. Nutr. Food Res. 2004, 270 – 281 Me The structural features of sweet and umami taste receptors !N-terminal extracellular domain (ECD) !7 transmembrance domains (TMD) !cysteine-rich domain (CRD) Orthosteric site (open to close) Taste signal transduction mechanisms !sweet or umami tastants bind to VFD which transform to closed state !C-terminal couples with G", G# or G$-gustducin proteins !G-gustducin proteins stimulate phospholipase C-#2 (PLC#2) !PLC#2 then hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) !decomposition to diacylglycerol (DAG) and inositol triphosphate (IP3) !IP3 activates IP3 receptors on endoplasmic reticulum (ER) !Ca2+ is released into plasma and activates Na+ channel !increased concentration of Na+ cause release of ATP into fibers !signal is finally intercepted by gustatory cortex in brain Front. Pharmacol. 11:587664. Curr. Opin. Clin. Nutr. Metab. Care 2017, 279 Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 O O O O Na+ Widely used artificial sweeteners S K+ S O NH O N- O- HO H S HO N Me N Me O O OH O H Cl HO Me O Cl O Me Cyclamate 1998-2018 HN O Saccharin Acesulfame-K acquisted by Firmenich® NH HO O O OMe 2 Me O O O OH Cl O Me stablize closed form Sucralose Neotame N NH2 NO2 H P-4000 Dulcin sweet taste enhancer O H O H N N sweet tastant O H O S N O S N O S N N Me Me O NH2 NH2 O Me NH O N Me N SE-3 2 H N O Me S617 S2218 Me DBU NH2 o O O O 160 C → r.t. CN + S HCl/EtOH Me H2N NH2 0 oC → r.t. HO then DMF N EDC, HOBt O O Me NaH, THF S H NO O2N H2N O 2 NaH, THF Boc O H2N Cl N 2 O S Me o o → lutidine, r.t. H N CN -30 C → r.t. -60 C r.t. 2 + N OH NC Me Me NC Me Me Me then then Me Me O Pd, H 40 psi O o NO2 2 NaOH 115 C NH O NH2 NHBoc 2 O NHBoc N C O H H H S, Et N NaOH, 100 oC O N 3 H2N S Ph N N S O EtOH, 80 oC S H O/EtOH Me 2 Me NC CN + Me Me N Me O O NC Dioxane, r.t. NC H2O/AcOH 0 oC → r.t. Me Me Me NH2 S2383 Baran Lab Cheng Bi Group Meeting Taste Enhancers and Blockers 01/30/21 N O O N Preliminary SAR study O O Me Me HO NH2 N N !the head structure is very important for efficacy HO H H !the hydrophobic structure in tail is beneficial N N O NH H H 2 !the the length of linker is also very important O NH2 NH2 Linker Bioorganic Med. Chem. Lett. 2020, 127000; ChemistrySelect 2020, 9457 Head Tail E% = 93±4.3 E% = 87±5.1 Common umami tastants Common enhancers: nucleotides O N O O O O O HO O O N OH N HO O Me HO P O N O OH OH HO OH HO O P NH HO O Me NH O NH NH N 2 2 2 O Me HO OH N NH HO OH L-Leucine Aspartic acid Glutamic acid Maltol NH2 guanosine monophosphate inosine monophosphate MeO OMe Br MeO OMe 1.carbodiimide MeO OMe HN N 2.thiosemicarbazide O aq. NaHCO N O 3 N NH HN NH2 S N HN N EtOH, heat OH S N MeO OMe S H WO 2006/084186 A2 FEMA 4798 In 1993, the first specific inhibitor for bitter taste was discovered. It is a lipo-protein made of phosphatidic acid (PA) and #-lactoglobulin (LG). Taste blockers: compounds that have no or little intrinsic taste but can dramatically inhibit the sensation of one or multiple of the five basic tastes. OH O O O H2N OH H2N N OH 4-Aminobutanoic acid HO O N︎,N︎-bis(carboxymethyl)-L-lysine With the assistance of computational model, the aforementioned two compounds that have similar binding to bitter receptors as quinine should Nature.