Functional Plant Science and Biotechnology ©2007 Global Science Books Lamiaceae Lectins Gerardo Pérez* • Nohora Vega Biochemistry Laboratory, Chemistry Department, Universidad Nacional de Colombia, Bogotá, Colombia Corresponding author : * [email protected] ABSTRACT The Lamiaceae family is widely distributed throughout the world and some species have been used in folk medicine, gastronomy and as a source of essential oils and aromas since ancient times; secondary metabolites from many species from Eurasia and North-America have been characterised during the last 5-6 decades. By contrast, species from the neotropical Calosphace Benth. subgenus have been little explored, despite their great diversity. Studies on seeds have been limited to mucilage distribution, chromosome patterns and, since the 1970s, to the presence of lectins, mainly in Salvia and Sclarea Benth. subgenera from the temperate zone. This review initially summarises the available information concerning the presence of lectins in both temperate and neotropic genera, the former being the subject of the pioneering work of Bird’s group in the 1970s which revealed the presence of seed lectins able to recognise the Tn antigen (GalNAc Ser/Thr). Later work has contributed to further our knowledge regarding neotropic genera lectins. The various detection methods used for assessing the presence of lectins in Lamiaceae seeds and vegetative tissues are discussed. The biochemical characteristics of lectins isolated from five genera (Salvia, Lepechinia, Moluccella, Glechoma and Clerodendron), their structural features and fine specificity are compared. Recent findings concerning their interactions with cell lines and Tn antigen-containing tumour cells are presented. An overview is given about their potential applications and those research lines which would help us in better understanding these lectins. _____________________________________________________________________________________________________________ Keywords: carbohydrate specificity, characterization, Clerodendron trichotomum, Glechoma hederacea, Lepechinia bullata, Moluccella laevis, Salvia bogotensis, Salvia sclarea, Tn Abbreviations: aBSM, asialo bovine submaxillary mucin; aOSM, asialo ovine submaxillary mucin; CELISA, Cell enzyme-linked immunosorbent assay; ELLSA, Enzyme-linked lectinosorbent assay; ECL, Erythrina corallodendron lectin; Gleheda, Glechoma hedera- cea lectin; GPs, glycoproteins; LBL, Lepechinia bullata lectin; MLL, Moluccella laevis lectin; RBCs, red blood cells; SBoL, Salvia bogotensis lectin; SPR, surface plasmon resonance; SSL, Salvia sclarea lectin; VVB4, Vicia villosa B4 isolectin CONTENTS INTRODUCTION...................................................................................................................................................................................... 288 LECTIN DETECTION METHODS .......................................................................................................................................................... 289 EARLY WORK ON LECTIN PROSPECTING IN CRUDE EXTRACTS................................................................................................ 290 RECENT WORK ON LECTIN PROSPECTING...................................................................................................................................... 291 ISOLATED AND CHARACTERISED LECTINS .................................................................................................................................... 291 Seed lectins............................................................................................................................................................................................ 292 Lectins from vegetative tissues.............................................................................................................................................................. 292 STRUCTURAL ASPECTS........................................................................................................................................................................ 293 FINE CARBOHYDRATE SPECIFICITY AND COMBINING SITES..................................................................................................... 293 Moluccella laevis lectin......................................................................................................................................................................... 294 Salvia sclarea lectin............................................................................................................................................................................... 294 Glechoma hederacea lectin ................................................................................................................................................................... 294 INTERACTIONS WITH CELLS .............................................................................................................................................................. 295 Cell binding and cytotoxic activity........................................................................................................................................................ 295 Mitogenic activity.................................................................................................................................................................................. 295 LECTINS AS TOOLS FOR TN ANTIGEN DETECTION IN TUMOUR CELLS ................................................................................... 296 FINAL REMARKS.................................................................................................................................................................................... 296 ACKNOWLEDGEMENTS ....................................................................................................................................................................... 296 REFERENCES........................................................................................................................................................................................... 296 _____________________________________________________________________________________________________________ INTRODUCTION analysing secondary metabolites, such as essential oils, ter- penoids , flavonoids and, more recently, antioxidants and The Lamiaceae family is widely distributed throughout the compounds having pharmacological activity (for a review, world, encompassing some 3,185 species following tradi- see Harley et al. 2004). tional circumscription. Due to the proposals of Cantino Reviewing databases from 1970 to the present has (1992), Cantino et al. (1992) and Wagstaff et al. (1998), revealed an increasing interest in the family, as about 570 this family has recently incorporated a substantial number articles out of the 2,000 to date have been published during of species formerly located in the Verbenaceae family, the last three years. Most studied species are from Eurasia bringing the total species’ number close to 7,170 (Harley et and North-America; during the previously-mentioned pe- al. 2004). Most studies on this family have been centred on riod only about 27 papers (up to July 30th 2007) dealt with Received: 31 July, 2007. Accepted: 31 September, 2007. Invited Review Functional Plant Science and Biotechnology 1(2), 288-299 ©2007 Global Science Books species from Africa and Central- and South-America. It is or irreversibly inactivate the supports used for purification. worth noting that despite its great diversity, species from For their part, pectins markedly increase solution viscosity, the neotropical Calosphace Benth. subgenus have been thereby reducing extraction efficiency and detection assay little explored. sensitivity. Contrasting with the numerous studies on secondary Several methods can be used for eliminating or redu- metabolites from aerial parts, little work has been done on cing pigments and pectins; for example thiourea in extrac- nutlets (seeds), dealing mainly with myxocarpy (mucilage tion buffer, treating extracts with DEAE-cellulose and di- presence) (Ryding 1992a, 1992b, 2001), morphology (Paton gestion with pectinases have been revealed to be very ef- 1992) and chromosome number (for references see Harley fective in improving lectin detection whilst keeping them and Heywood 1992). Knowledge regarding constituents soluble (Fernández-Alonso et al. 2003). such as proteins, carbohydrates or nucleic acids remains vir- Erythrocyte agglutination has been by far the most tually a “no man’s land”. widely used method for lectin detection; however, most Amongst the proteins, lectins represent a group whose Lamiaceae lectins recognise, among naturally-occurring definition has evolved from purely factual criteria, such as human red blood cells (RBCs), those cells present in indivi- “…a sugar-binding protein or glycoprotein of non-immune duals suffering from the “polyagglutinability syndrome” origin which agglutinates cells and/or precipitates glyco- which is very rare; this severe restriction may be overcome conjugates,” (Goldstein et al. 1980) to structural/functional by enzymatically treating A-type erythrocytes (Hirohashi et criteria defining them as being, “…proteins possessing at al. 1985) or rabbit erythrocytes (Peumans et al. 1996), least one non-catalytic domain, which binds reversibly to a thereby exposing the Tn antigen (GalNAc Ser/Thr) which specific mono- or oligosaccharide” (Peumans and van Dam-