The naturally occurring furanones: formation and function from pheromone to food

Jc. Slaughter, The naturally occurring furanones: formation and function from pheromone to food, BIOL REV, 74(3), 1999, pp. 259-276
Citations number
Categorie Soggetti
Biology,"Experimental Biology
Journal title
ISSN journal
1464-7931 → ACNP
Year of publication
259 - 276
SICI code
Three closely related 4-hydroxy-3 (2H)-furanones have been found in a range of highly cooked foodstuffs where they are important flavour compounds wit h aroma threshold values as low as 20 mu g kg(-1) water (approximately 0.14 mu mol l(-1)). The compounds are formed mainly as a result of the operatio n of the Maillard reactions between sugars and amino acids during heating b ut one compound, 5-(or 2)-ethyl-2-(or 5)-methyl-4-hydroxy-3 (2H)-furanone, appears in practice to be produced by yeast, probably from a Maillard inter mediate, during the fermentation stages in the production of soy sauce and beer. The compounds are also important in the flavour of strawberry, raspbe rry, pineapple and tomato but the route of biosynthesis is unknown. Two 3-h ydroxy-2 (5H)-furanones, emoxyfuranone and sotolon, which are produced spon taneously from amino acids such as threonine and 4-hydroxy-L-leucine are ma jor contributors to meaty and spicy/nutty flavours in foods. The biosynthes is of 5-(1,2-dihydroxyethyl)-3,4-dihydroxy-2 (5H)-furanone (ascorbic acid, vitamin C) and 5-hydroxymethyl-3,4-dihydroxy-2(5H)-furanone (erythro-ascorb ic acid) from sugars in plants and yeast, respectively, has been characteri zed to the enzymic level. After treatment with chlorine, humic waters conta in a range of chloro-furanones, some of which, particularly 3-chloro- 4-(di chloromethyl)-5-hydroxy-2 (5H)-furanone (MX), are powerful mutagens. The fu ranones which occur in foods are also mutagenic to bacteria and cause DNA d amage in laboratory tests. However, these compounds are, in practice, very effective anti-carcinogenic agents in the diets of animals which are being treated with known cancer-inducing compounds such as benzo[alpha]pyrene or azoxymethane. Two of the food-derived furanones have antioxidant activity c omparable to that of ascorbic acid. A biological function has been discover ed for some of the furanones besides vitamin C. 5-Methyl-4-hydroxy-3 (2H)-f uranone is a male pheromone in the cockroach Eurycolis-florionda (Walker) a nd the 2,5-dimethyl derivative deters fungal growth on strawberries and is an important component of the attractive aroma of the fruit. The red seawee d Delisea pulchra (Greville) Montagne produces a range of brominated furano nes which prevent colonisation of the plant by bacteria by interfering with the acylated homoserine lactone (AHL) signalling system used by the bacter ia for quorum sensing, In addition, these compounds can deter grazing by ma rine herbivores. It is proposed here that the evolved biological function o f a number of furanones is to act as inter-organism signal molecules in sev eral different systems. This has resulted in two coincidental effects which are important for humans. Firstly, the easily oxidized nature of the furan ones in general, which is likely to be an important property in their funct ioning as signal molecules, results in both mutagenic and anti-carcinogenic activity. The balance of these two effects from compounds in the diet has yet to be fully established. Secondly, and more specifically, the 4-hydroxy -3 (2H)-furanones associated with fruit aromas act to attract animals to th e fruit, which ensures seed dispersal. In the case of humans, the coinciden tal synthesis of some of these compounds in foods during preparation result s in these foods appearing particularly attractive through the transferred operation of the original signalling mechanisms.