Interest in guaraná, Paullinia cupana H.B.K. variety sorbilis (Mart.) Ducke (Sapindaceae), has intensified recently as its use in western Europe and North America has increased (Bempong & Houghton, 1992). Guaraná is a Brazilian plant presently employed widely in its country of origin to flavour carbonated soft drinks. Over 20 different brands of guaraná drinks are sold in Brazil alone (Müller, 1998). It is gaining popularity world wide as a stimulant under this and other forms, such as powders, pills, capsules, hard and soft candies, etc. It is also often a main ingredient in "smart drinks" available at raves. Guaraná was once considered a drug substance in the United States, but is currently classified as a food substance and dietary supplement (Carlson & Thompson, 1998). The potential abuse through unregulated consumption of this stimulant product, which can contain up to 8% caffeine, has prompted some concern, notably in Germany (Lautenbacher, 1994). Due to the "rapid and significant increase" in guaraná consumption in the United Kingdom, the Advisory Committee on Novel Foods and Processes (ACNFP) in the UK has recently reviewed guaranás safety-in-food use (Tomlinson, 1993 a) but concluded that the levels of caffeine in various guaraná products do not give rise to safety concerns. It is interesting to note that the world wide interest in guaraná has not gone unnoticed by multinational companies, such as The Coca-Cola Company and Pepsi Co. Both now produce guaraná drinks: Tai and Josta respectively (Müller, 1996 a).

Guaraná, a creeping shrub native to the Manaus and Parintins regions of the Amazon, has a long historical use, and its cultivation predates the discovery of South America by Europeans (Taylor, 1998). Its common name is derived from the Guaranis Indians, one of the numerous indigenous tribes who have cultivated guaraná for centuries, and continue to do so today (Garcia, 1996). Duke and Vasquez (1994) include the following as past and present tribal uses of guaraná: analgesic, astringent, febrifuge, and stimulant. Guaraná tonic is used to treat diarrhoea, hypertension, migraine, neuralgia, and dysentery (Duke & Vasquez, 1994). It is also reputed to be a cardiovascular drug and to prevent arteriosclerosis (Duke & Vasquez, 1994). guaraná is also thought to ward off headaches and relieve cramps (Spear, 1997).

Modern uses of guaraná do not differ much from traditional ones, but some notable additions do exist: aphrodisiac and mind expanding properties have been added to the list. Another addition is the use of guaraná as a diet aid. Though all three claims seem somewhat dubious, and aimed simply at catching the consumers eye (and money), the use of guaraná as a diet aid could be extrapolated from Miura et al.s study of the effects of guaraná on exercise in normal and epinephrine-induced glycogenolytic mice (1998). In this study, a water extract of guaraná (500 mg/kg) increased the blood glucose level and decreased the liver glycogen contents of mice 60 min after oral maltose administration. Effectively inducing normal mice use up their glycogen reserves more rapidly. It also significantly suppressed exercise-induced hypoglycemia. However, the water extract of guaraná did not affect the blood glucose in epinephrine-induced glycogenolytic and exercise mice. These findings indicate that the suppressive mechanism of hyopglycemia might be due to the promotion of glycogen resolution (Miura, et al., 1998). In other words, guaraná helped free up glycogen from the liver, and make its energy readily available as glucose in the blood. The use of guaraná as a diet aid can be extrapolated from these results, however, it not clear whether guaraná would have an equivalent effect in humans, and what the recommended dose would be for such a use. These results may also lend support to the claims that guaraná is a good energy source: thought the guaraná itself is not that source, it frees up the energy reserves (glycogen) of an individual, thereby providing the individual with energy.

Studies of the chemical composition of guaraná started as early as 1826, when von Matius isolated a white crystalline substance from guaraná: guaranine (now know as caffeine). Among guaranás primary identified pharmacologically active constituents, we find various methylxanthine alkaloids, notably caffeine, theobromine and theophylline (Carlson & Thompson, 1998; Belliardo, 1985). Other chemical compounds include the polyphenols (+)-catechin and (-)-epicatechin (Carlson & Thompson, 1998). The essential oil from guaraná was found to contain 2 methylbenzenes, 1 cyclic monoterpene, 2 cyclic sequiterpene hydrocarbons, 2 methoxyphenylpropenes and 2 alkylphenol derivatives (Benoni et al., 1996).

Some claims of psychoactivity of the essential oil have been noted, and were presumed to be associated with the identified constituents estragole (4-methoxyamphetamine) and anthole (tert-aminiketones). However, neither of these psychoactive compounds could be traced in human urine after oral administration on the essential oil, and therefor any psychoactivity of the essential oil of guaraná can be excluded (Benoni et al. 1996).

The claims of sustained stimulation derived from guaraná have been thought to be associated with a differential release and/or uptake of caffeine from guaraná. This association has been disproved by Bempong and Houghton (1992), who observed that release and uptake of caffeine from guaraná preparations are the same as for preparations containing free caffeine. However, this sustained effect may be due to the as-of-yet un-investigated effects of the two other stimulants found in guaraná, namely theobromine and theophylline, or potentially to guaranás saponin content. Theobromine is a stimulant/euphoric, also found in chocolate, and theophylline is a stimulant stronger than caffeine, but present in smaller amounts in guaraná (Spear, 1997; Carlson & Thompson, 1998). Ginseng-derived saponins have a similar sustained-stimulant effect when taken over an extended time span (Spear, 1997).

Claims that guaraná has beneficial effects on memory, concentration and endurance are both supported and refuted by current research. Espinola et al. (1997) report a positive effect of both single (3.0 and 30.0 mg/kg) and chronic administrations (0.3 mg/ml) of guaraná on memory acquisition in mice and rats. They also observed low guaraná toxicity, even after 23 months of administration (Espinola et al., 1997). In their study of toxic behavioural effects of guaraná in laboratory animals, Mattei et al. (1998) discovered that guaraná has an antioxidant effect, even at low concentrations (1.2 mg/ml), but also that it had no effect on motor activity and did not alter the hypnotic effect of pentobarbital at higher concentrations (250-1000 mg/kg i.p.). On the other hand, Espinola et al. (1997) reported significant increases in physical capacity of mice given a guaraná suspension in a dose of 0.3 mg/ml when subjected to stressful situations such as forced swimming, after 100 and 200 days of treatment. Such an effect, however, was not obtained with a concentration of 3.0 mg/ml, nor with the ingestion of a suspension of ginseng 5.0 mg/ml, nor of a solution of caffeine 0.1 mg/ml. Galduroz & Carlini twice (1994; 1996) studied the effects of guaraná on cognition in humans (short and long term administration), and came up with negative results. They also conclude that guaraná cannot be thought of as "harmless". Santa Maria et al. (1998) studied the toxicity of guaraná in vitro bioassays, and concluded that the concentration of guaraná is of critical importance in its cytotoxic activity, and that high dosed may be harmful to human health. Mattei et al. (1998) demonstrated an absence of toxicity of guaraná in rats and mice who had been receiving regular doses of guaraná over the course of the study.

Based on a claim by tribal users that guaraná thins the blood, Bydlowski et al. (1988) studied the effects of aqueous extracts of guaraná on the aggregation of human and rabbit platelets. guaraná extracts were shown to have anti-aggregatory and de-aggregatory actions on platelet aggregation induced by ADP or arachidonate but not by collagen, and inhibited platelet aggregation in rabbits following either intravenous or oral administration. A later study (Bydlowski et al., 1991) found that guaraná extract and TCL separated fractions decreased platelet aggregation and platelet thromboxane formatin from {14C}-arachidonic acid. It was concluded that the antiaggregatory action of guaraná may be due in part to the decreased thromboxane syntheses.

Guaranás tannic acid content could probably account for its use as a digestive tonic (Spear, 1997), but also raises some concerns about its use as tannins are increasingly recognised anti-nutrients and dietary carcinogens (Morton, 1992). Special care has to be taken when preparing guaraná so as to avoid oxidizing the phenolic substances in the seeds, which leads to the seeds turning black in colour, bitter in taste, and irritating the gastrointestinal tract (Henmann, 1982).

In conjunction with its rise in popularity, other recent studies have focused on the effect of guaraná on tooth decay (Pinheiro et al., 1987; Grando et al., 1996) and the ecological and social aspects of guaraná, its cultivation and use (Henman, 1982; Katzung, 1993). The presence and purity of guaraná in commercially available products (Hoffmann et al., 1997; Thomlinson, 1993 a & b) has also been studied. This is of interest here, as results and chromatographic profiles of 14 commercial products in solid dosage form indicate that a number of these products may not contain guaraná as an active ingredient or contain less than the declared quantity of guaraná (Carlson & Thompson, 1998). Consequently, one should make sure to buy guaraná products from a reputable dealer. Though some claims for the use of guaraná are obviously "out there" (i.e., as an aphrodisiac), many other traditional and modern uses, namely that of guaraná as a stimulant and energy booster, are well documented and researched. The low toxicity of guaraná makes it an attractive medicinal plant, and it seems to me that the benefits to be drawn from its use (especially by deadline hounded University students) outweigh any qualms I would have about taking it.

References

Belliardo, F., Martelli, A. and Valle, M.G. (1985) HPLC determination of caffeine and theophylline in Paullinia cupana Kunth (guaraná) and Cola spp. samples. Z Lebensm Unters Forsch May 180(5): 398-401.

Bempong, D.K. and Houghton, P.J. (1992) Dissolution and absorption of caffeine from guaraná. J Pharm Pharmacol. Sept. 44(9): 769-71.

Benoni, H., Dallakian, P. and Taraz, K. (1996) Studies on the essential oil from guaraná. Z Lebensm Unters Forsch Jul. 203(1): 95-8.

Bydlowski, S.P., Yunker, R.L. and Subbiah, M.T. (1988) An novel property of guaraná extract (Paullinia cupana): inhibition of platelet aggregation in vitro and in vivo. Braz J Med Biol Res 24(4): 421-4

Bydlowski, S.P., DAmico, E.A. and Chamone, D.A. (1991) An aqueous extract of guaraná (Paullinia cupana) decreases platelet thromboxane synthesis. Braz J Med Biol Res 24(4): 421-4

Carlson, M. and Thompson, R.D. (1998) Liquid chromatographic determination of methylxanthines and catechins in herbal preparations containing guaraná. J AOAC Int. Jul-Aug. 81(4): 691-701.

Duke, James A. and Vasquez, Rodolfo. (1994) Amazonian. Sited in Taylor (1998).

Espinola, E.B., Dias, R.F., Mattei, R., and Carlini, E.A. (1997) Pharmacological activity of guaraná (Paullinia cupana Mart.) in laboratory animals. J Ethnopharmacol Feb. 55(3): 223-9

Hoffmann, F.L., Garcia-Cruz, C.H., Vinturim, T.M., and Pagocca, F.C. (1997) Survey of the microbial quality of nonalcoholic carbonated beverages. Folia Microbiol (Praha) 42(3): 199-202.

Galduroz, J.C. and Carlini, E. de A. (1994) Acute effects of the Paullinia cupana, "Guaraná" on the cognition of normal volunteers. Rev Paul Med. Jul-Sep. 112(3): 607-11.

Galduroz, J.C. and Carlini, E. de A. (1996) The effects of long-term administration of guaraná on the cognition of normal, elderly volunteers. Rev Paul Med. Jan-Feb. 114(1): 1073-8.

Garcia, Marcos. (1996) O Cultivo do guaranázeiro. Embrapa-CPAA, Manaus, Brazil http://www.cr-am.rnp.br/embrapa/guaraná.html

Grando, L.J., Tames, D.R., Cardoso, A.C., and Gabilan, N.H. (1996) In vitro study of the enamel erosion caused by soft drinks and lemon juice in deciduous teeth analyses by stereomicroscopy and scanning electron microscope. Caries Res 30(5): 373-8.

Henmann, A.R. (1982) guaraná (Paullinia cupana var. sorbilis): ecological and social; perspectives on an economic plant of the central Amazon basin. J Ethnopharmacol Nov 6(3): 311-38.

Katzung, W. (1993) guaraná: a natural product with high caffeine content. Med Monatsschr Pharm Nov. 16(11): 330-3

Lautenbacher, L. (1994) guaraná-Wundermittel oder Genußmittle? Deutsche Apoteker Zeitung. 134(31): 27-31.

Mattei, R., Dias, R.F., Espinola, E.B., Carlini, E.A, and Barros, S.B. (1998) guaraná (Paullinia cupana): toxic behavioral effects in laboratory animals and antioxidants activity in vitro. J Ethnopharmacol. Mar. 60(2): 111-6

Miura, T., Tatara, M, Nakamura, K., and Suzuki, I. (1998) Effects of guaraná on exercise in normal and epinephrine-induced glycogenolytic mice. Biol Pharm Bull. Jun. 21(6): 646-8.

Müller, Marcelo. (1996 a) Josta, guaraná imitção. http://www.symmetrix.ch/Public/guaraná/ under "Stories".

Müller, Marcelo. (1996 b) What is guaraná? http://www.symmetrix.ch/Public/guaraná/ukdocs/whatis.html

Müller, Marcelo. (1998) What is the best guaraná soft drink? http://www.symmetrix.ch/Public/guaraná/ under "Best".

Morton, J.F. (1992) Widespread tannin intake via stimulants and masticatories, especially guaraná, kola nut, betel vine, and accessories. Basic Life Sci 59: 739-65.

Pinheiro, C.E., de Oliveira, S.S., da Silva, S.S., Poletto, M.I. and Pinheiro, C.F. (1987) Effect of guaraná and Stevia Rebaudiana Bertoni (leaves) extracts, and stevoside, on the fermentation and synthesis of extracellular insoluble polysaccharides of dental plaque. Rev Odontol Univ Sao Paulo Oct-Dec 1(4): 9-13.

Santa Maria, A., Lopez, A., Diaz, M.M., Munoz-Mingarro, D., and Pozuelo, J.M. (1998) Evaluation of the toxicity of guaraná with in vitro bioassays. Ecotoxicol Environ Saf. Mar. 39(3): 164-7.

Spear, D.Read. (1997) guaraná: Product Research. Whole Health Discount Center. http://www.pyruvate1.com/products/gu/.

Taylor, Leslie. (1998) Herbal Secrets of the Rainforest. Prima Publishing. Austin, Tx. 288 pp.

Tomlinson, Nick. (1993 a) MAFF UK- Caffeine in guaraná Products. Joint Food Safety and Standards Group Food Surveillance Information Sheet Number 21, Dec. 1993. http://www.gov.gov.uk/food/infosheet/1993/no21/21caff.htm

Tomlinson, Nick. (1993 b) supplemental table to MAFF UK- Caffeine in guaraná Products. Joint Food Safety and Standards Group Food Surveillance Information Sheet Number 21, Dec. 1993. http://www.gov.gov.uk/food/infosheet/1993/no21/table.htm#table

von Martius, T. (1826) Die Zusammensetzung des Guaranins. Lieb. Ann. 36: 93-95.