Crude extracts of a callus culture (two culture media) and adult plants (two collections) from Alternanthera tenella Colla (Amaranthaceae) were evaluated for their antibacterial and antifungal activity, in order to investigate the maintenance of antimicrobial activity of the extracts obtained from plants in vivo and in vitro. The antibacterial and antifungal activity was determined against thirty strains of microorganisms including Gram-positive and Gram-negative bacteria, yeasts and dermatophytes. Ethanolic and hexanic extracts of adult plants collected during the same period of the years 1997 and 2002 [Ribeirão Preto (SP), collections 1 and 2] and obtained from plant cell callus culture in two different hormonal media (AtT43 and AtT11) inhibited the growth of bacteria, yeasts and dermatophytes with inhibition halos between 6 and 20 mm. For the crude extracts of adult plants bioassay-guided fractionation, purification, and isolation were performed by chromatographic methods, and the structures of the isolated compounds were established by analysis of chemical and spectral evidences (UV, IR, NMR and ES-MS). Steroids, saponins and flavonoids (aglycones and C-glycosides) were isolated. The minimum inhibitory concentration (MIC) of the isolated compounds varied from 50 to 500 μg/mL. © 2009 Verlag der Zeitschrift für Naturforschung, Tübingen.645-6373381Agrawal, P.K., (1989) Carbon-13 NMR of Flavonoids, p. 564. , Elsevier, AmsterdamAlfermann, A.W., Petersen, M., Natural product formation by plant cell biotechnology (1995) Plant Cell, Tissue Organ Cult, 43, pp. 199-205Ames, T.T., Worden, R.M., Continuous production of daidzein and genistein from soybean in a magnetofluidized bed bioreactor (1997) Biotechnol. Prog, 13, pp. 336-339Aquino, R., Morelli, S., Lauro, M.R., Abdo, S., Saija, A., Tomaino, A., Phenolic constituents and antioxidant activity of an extract of Anthurium versi-color leaves (2001) J. Nat. Prod, 64, pp. 1019-1023Avancini, G., Abreu, I.N., Saldanha, M.D.A., Mohamed, R.S., Mazzafera, P., Induction of pilocarpine formation in jaborandi leaves by salicylic acid and methyljasmonate (2003) Phytochemistry, 63, pp. 171-175Biela, C.A., Salvador, M.J., Dias, D.A., Baruffi, M.D., Pereira-Crott, L.S., Immunomodulatory and anti-inflammatory activities and phytochemical screening of Alternanthera tenella Colla aqueous extracts (2008) Mem. Inst. Oswaldo Cruz, 103, pp. 569-577Bouque, V., Bourgaud, F., Nguyen, C., Guckert, A., Production of daidzein by callus cultures of Psoralea species and comparison with plants (1998) Plant Cell, Tissue Organ Cult, 53, pp. 35-41Bourgaud, F., Gravot, A., Milesi, S., Gontier, E., Production of plant secondary metabolites: A historical perspective (2001) Plant Sci, 161, pp. 839-851Cai, Y., Sun, M., Corke, H., Antioxidant activity of betalains from plants of Amaranthaceae (2003) J. Agric. Food Chem, 51, pp. 2288-2294Chattopadhay, D., Maiti, K., Kundu, A.P., Chakraborty, M.S., Bhadra, R., Mandal, S.C., Mandal, A.B., Antimicrobial activity of Alstonia macrophylla: A folklore of bay islands (2001) J. Ethnopharmacol, 77, pp. 49-55Chaurasia, N., Swichtl, M., Sterols and steryl glycosides from Urtica dioica (1987) J. Nat. Prod, 50, pp. 881-885Cohen, M.L., Epidemiology of drug resistance: Implications for a post-antimicrobial era (1992) Science, 257, pp. 1050-1055Cushnie, T.P.T., Lamb, A.J., Antimicrobial activity of flavonoids (2005) I. J. Antimicrob. Agents, 26, pp. 346-356Espinel-Ingroff, A., Dawson, K., Pfaller, M., Anaissie, E., Breslin, B., Dixon, D., Fothergill, A., Walsh, T., Comparative and collaborative evaluation of standardization of antifungal susceptibility testing for filamentous fungi (1995) Antimicrob. Agents Chemother, 39, pp. 314-319Ferreira, E.O., Salvador, M.J., Pral, E.M.F., Alfieri, S.C., Ito, I.Y., Dias, D.A., A new hepta- substituted (E)-aurone glucoside and other aromatic compounds from Gomphrena agrestis with biological activity (2004) Z. Naturforsch, 59 c, pp. 499-505Fu, T.J., Singh, G., Curtis, W.R., (1999) Plant Cell Culture for the Production of Food Ingredients, , Kluwer Academic Publishers, New YorkGamborg, O.L., Phillips, G.C., (1995) Plant Cell, Tissue and Organ Culture - Fundamental Methods, , Springer Publishers, New YorkGrove, D.C., Randall, W.A., (1955) Assay Methods of Antibiotics: a Laboratory Manual (Antibiotics Monographs, 02), , Medical Encyclopedia Inc., New YorkHarborne, J.B., (1996) The Flavonoids: Advances in Research since 1986, , Chapman and Hall, LondonKojima, H., Noriko, S., Akiko, H., Haruo, O., Sterol glucosides from Prunella vulgaris (1990) Phytochemistry, 29, pp. 2351-355Markam, K.R., Geiger, H., 1H nuclear magnetic resonance spectroscopy of flavonoids and their glycosides in hexadeuterodimethylsufoxide (1994) The Flavonoids, pp. 450-453. , (Harborne J. B., ed.). Chapman and Hall, LondonMoraes, V.L.G., Santos, L.F.M., Castro, S.B., Loureiro, L.H., Lima, O.A., Souza, M.L.M., Yien, L.M.K., Costa, S.S., Inhibition of lymphocyte activation by extracts and fractions of Kalanchoe, Alternanthera, Paullinia and Mikania species (1994) Phytomedicine, 1, pp. 199-204Murashige, T., Skoog, F., A revised medium for rapid growth and bioassays with tobacco tissue culture (1962) Plant Physiol, 15, pp. 473-497(1993) Methods for dilution in antimicrobial susceptibility tests, , National Committee for Clinical Laboratory Standards, Approved standard M2-A5. National Committee for Clinical Laboratory Standards, Villanova, PA, USA(1998) Reference method for broth dilution antifungal susceptibility testing of conidium-forming filamentous fungi, , National Committee for Clinical Laboratory Standards, Proposed standard M38-P. National Committee for Clinical Laboratory Standards, Wayne(2003) Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, , National Commitee for Clinical Laboratory Standards, Approved Standard M7-A6. National Commitee for Clinical Laboratory Standards, WayneOtsuka, N., Liu, M.H., Shiota, S., Ogawa, W., Kuroda, T., Hatano, T., Tsuchiya, T., Anti-methicillin resistant Staphylococcus aureus (MRSA) compounds isolated from Laurus bobilis (2008) Biol. Pharm. Bull, 31, pp. 1794-1797Panizzi, L., Caponi, C., Catalano, S., Cioni, P.L., Morelli, I., In vitro antimicrobial activity of extracts and isolated constituents of Rubus ulmifolius (2002) J. Eth- nopharmacol, 79, pp. 165-168Penna, C., Marino, S., Vivot, E., Cruañes, M.C., Muñoz, J.D., Cruañes, J., Ferraro, G., Martino, V., Antimicrobial activity of Argentine plants used in the treatment of infectious diseases. Isolation of active compounds from Sebastiania brasiliensis (2001) J. Ethnopharmacol, 77, pp. 37-40Pomilio, A.B., Buschi, C.A., Tomes, C.N., Viale, A.A., Antimicrobial constituents of Gomphrena martiana and Gomphrena boliviana (1992) J. Ethnophar- macol, 36, pp. 155-161Pujol, I., Guarro, J., Llop, C., Soler, L., Fernández-Ballart, J., Comparison study of broth macrodilution and microdilution antifungal susceptibility tests for the filamentous fungi (1996) Antimicrob. Agents Chemother, 40, pp. 2106-2110Quiroga, E.N., Sampietro, A.R., Vattuone, M.A., Screening antifungal activities of selected medicinal plants (2001) J. Ethnopharmacol, 74, pp. 89-96Rauha, J.P., Remes, S., Heinonen, M., Hopia, A., Kahkonen, M., Kuyala, T., Pihlaya, K., Vuorela, P., Antimicrobial effects of Finnish plant extracts containing flavonoids and other phenolic compounds (2000) I. J. Food Microbiol, 56, pp. 3-12Salvador, M.J., Ferreira, E.O., Pral, E.M.F., Alfieri, S.C., Albuquerque, S., Ito, I.Y., Dias, D.A., Bioactivity of crude extracts and some constituents of Blutaparon portulacoides (Amaranthaceae) (2002) Phytomedicine, 9, pp. 566-571Salvador, M.J., Pereira, P.S., Franca, S.C., Candido, R.C., Ito, I.Y., Dias, D.A., Comparative study of antibacterial and antifungal activity of callus culture and adult plants extracts from Alternanthera maritima (Amaranthaceae) (2003) Braz. J. Microbiol, 34, pp. 131-136Salvador, M.J., Zucchi, O.L.A.D., Candido, R.C., Ito, I.Y., Dias, D.A., In vitro antimicrobial activity of crude extracts and isolated constituents of Alternanthera maritima (Amaranthaceae) (2004) Pharm. Biol, 42, pp. 138-148Salvador, M.J., Ferreira, E.O., Mertens-Talcott, S.U., Castro, W.V., Butterweck, V., Derendorf, H., Dias, D.A., Isolation and HPLC quantitative analysis of antioxidant flavonoids from Alternanthera tenella Colla (2006) Z. Naturforsch, 61 c, pp. 19-25Siqueira, J.C., Importância alimentícia e medicinal das Amaranthaceaes do Brasil (1987) Acta Biol. Leopoldensia, 9, pp. 5-22Siqueira, J.C., Phytogeography of Brazilian Amaranthaceae (1994) Pesq. Botânica, 0, pp. 5-21Siqueira, J.C., Guimarães, E.F., Amaran- thaceae do Rio de Janeiro - gênero Alternanthera Forsskal (1984) Rodriguésia, 36, pp. 21-40Stefanello, M.E., Cervi, A.C., Ito, I.Y., Salvador, M.J., Wisniewski Jr., A., Simionatto, E.L., Chemical composition and antimicrobial activity of essential oils of Eugenia chlorophylla (Myrtaceae) (2008) J. Essent. Oil Res, 20, pp. 75-78Tereschuk, M.L., Riera, M.V.Q., Abdala, L.R., Antimicrobial activity of flavonoids from leaves of Tagetes minuta (1997) J. Ethnopharmacol, 56, pp. 227-232Thien, B., Goslinska, O., Antimicrobial activity of Solidago virgaurea L. from in vitro cultures (2002) Fitoterapia, 73, pp. 514-516Tundis, R., Loizzo, M.R., Bonesi, M., Menichini, F., Statti, G.A., Menichini, F., In vitro cytotoxic activity of Salsola oppositifolia Desf. (Amaranthaceae) in a panel of tumor cell lines (2008) Z. Naturforsch, 63 c, pp. 347-354Wongwicha, W., Tanaka, H., Shoyama, Y., Tuvshintogto, K.H., Putalun, W., Production of glycyrrhizin in callus cultures of Licorice (2008) Z. Naturforsch, 63 c, pp. 413-417Yayli, N., Seymen, H., Baltaci, C., Flavone C- glycosides from Scleranthus uncinatus (2001) Phytochemistry, 58, pp. 607-610Zhou, B., Blaskò, G., Cordell, G.A., Alternanthin, a C-glycosylated flavonoid from Alternanthera philoxeroides (1988) Phytochemistry, 27, pp. 3633-3636