Abstract
Context: Xanthosoma sagittifolium Schott. (Araceae) and Laportea aestuans (L.) Chew (Urticaceae) are two medicinal species used as food and to prevent and treat bone diseases, such as osteoporosis, in traditional Brazilian medicine.
Objective: To investigate the free calcium concentration and further support the traditional use of these species as medicine.
Materials and methods: L. aestuans and X. sagittifolium leaves were dehydrated and cooked to evaluate the presence of free calcium. The total oxalate content was determined by heat digestion in H2SO4, oxalate precipitation with CaCl2 and permanganate titration.
Results: The calcium content found in L. aestuans was quite significant (638.00 mg/100 g), whereas the fresh and cooked leaves of X. sagittifolium demonstrated a low content of calcium, at 273.17 and 369.81 mg/100 g, respectively.
Discussion and conclusion: The use of this species for the prevention and treatment of bone diseases is in agreement with the results of the free calcium (Ca++) analyses. Our data show that each species may be used as a health supplement in poor communities, provided that studies validate their safe use.
Keywords::
Introduction
Osteoporosis is characterized by a net loss of bone (CitationOcchiuto et al. 2006). There is evidence that medicinal plants, dietary products, and natural pure compounds can benefit bone metabolism (CitationPutnam et al. 2007). In Brazilian popular medicine (Pernambuco state, Northeast region), Laportea aestuans (L.) Chew (Urticaceae) and Xanthosoma sagittifolium Schott. (Araceae), known locally as “urtiga-vermelha” and “taioba”, respectively, are used to reduce the symptoms of osteoporosis.
Xanthosoma sagittifolium is a species that originated from tropical America and cultivated in several countries of Asia and Africa as a subsistence food crop (CitationAlamu & McDavid, 1978; CitationGiacometti & Léon, 1994). It is known that X. sagittifolium contains calcium oxalate crystals (raphides) that can penetrate soft skin (CitationBradbury & Nixon, 1998) and have been associated with its acridity and toxicity (CitationSefa-Dedeh & Agyir-Sackey, 2004). Oxalates are also known to interfere with the bioavailability of calcium (CitationFink 1991). However, no reports were found in the literature concerning the use of X. sagittifolium for the treatment of osteoporosis.
Laportea aestuans is an erect annual herb covered with glandular and stinging trichomes. To our knowledge, there is only one study that shows the indication of L. aestuans as a supplement for calcium. In the southwestern region of Cameroon, the decoction of different parts of L. aestuans is used for treating anemia, low calcium, fibroids, and dermatitis (Jiofack et al. Citation2009). Curiously, the edible giant snail, Achatina achatina L. (Gastropoda: Achatinidae), also consumes the leaves of L. aestuans and Xanthosoma mafaffa Schott, another Araceae species that also contains crystals of calcium oxalate (CitationOtchoumou et al. 2005). According to CitationBabalola and Akinsoyinu (2009), snail meat is rich in calcium, and the high content of calcium in these snails suggests that the consumption of snails can increase calcium in the body.
CESAM is a Popular Health Center located in the northeastern region of Brazil (Pernambuco state). Considering the local importance of CESAM, there is an urgent need to standardize the activities carried out there and to adjust them to the criteria of the Brazilian agency that controls the handling, distribution and commercialization of food, cosmetics, herbal medicines and allopathic drugs (Agência Nacional de Vigilância Sanitária − ANVISA). Many of the phytomedicines from CESAM are already sold in the local markets. However, for the safe and effective use of medicines, the quality/standardization in their composition and the verification of the bioactivity are essential requirements. Currently, the herbal drugs from CESAM fail to meet these standards.
The members of CESAM have suggested that L. aestuans and X. sagittifolium been studied because both are indicated for the prevention and treatment of bone diseases yet are toxic if not used correctly. During the study, the following three questions were addressed: 1) Does L. aestuans and X. sagittifolium, which are indicated for the treatment and prevention of such bone diseases as osteoporosis, have enough Ca++ to justify their traditional use?; 2) Does the cooking, which is highly recommended by specialists, of X. sagittifolium leaves diminish the oxalate content? and 3) Does the heating process of L. aestuans leaves cause the disintegration of the trichomes and allow for its dietary use? The present study attempts to answer these three questions.
Materials and methods
Study area
The study was carried out in the Muribeca community, a low-income neighborhood in the city of Jaboatão dos Guararapes (8° 6′ 46″ S, 35° 0′ 54″ W). Specialists of CESAM have indicated two species (L. aestuans and X. sagittifolium) among the 44 medicinal plant species cultivated as medicines that are used to reduce the symptoms of osteoporosis. Voucher specimens of L. aestuans and X. sagittifolium were collected with the aid of CESAM members, identified by Dr. Laise de Holanda Cavalcanti Andrade (Department of Botany, Federal University of Pernambuco), and deposited at the UFP Herbarium under numbers 43709 and 43815, respectively.
Calcium determination
Fresh X. sagittifolium and L. aestuans leaves were, respectively, cooked at 90°C for 1 h and dehydrated in a domestic oven at 105°C for 24 h. The oxalate content was determined using three steps: digestion, oxalate precipitation and permanganate titration (CitationIwuoha & Kalu, 1995). In brief, the calcium content was determined following precipitation in acidic medium as an insoluble calcium oxalate. The precipitate was dissolved in dilute sulfuric acid and heated, and the oxalic acid released was titrated with potassium permanganate solution at 60°C. The procedure was performed at the Food Experimentation and Analysis Laboratory (Nutrition Department, UFPE, Brazil). The data are presented as mg calcium/100 g.
Results and discussion
A survey of the specialized literature about traditional medicine revealed no information on the use of X. sagittifolium as medicine. In contrast, the leaves of L. aestuans are used for treating diabetes mellitus (CitationLans et al. 2006), reproductive problems, such as infertility, menstrual and childbirth pain and for shortening labor (CitationLans et al. 2007), anemia, fibroids, dermatitis, and low calcium (Jiofack et al. Citation2009).
The concentration of free calcium (Ca++) found in the dry leaves (638.00 mg/100 g) of L. aestuans was quite significant, considering that the recommended daily intake is 800 mg (CitationNational Research Council, 1981). This concentration can justify the traditional use of the leaves of this species in the prevention and treatment of bone diseases, including osteoporosis, as recommended by CESAM. The specialists recommend adding powdered leaves to beans or to another type of food as a dietary calcium supplement that can be used daily during meals. Considering the indication of 800 mg of calcium per day, 126 g of dry L. aestuans leaves could fulfill this daily requirement, as 100 g provides 79.75% of this allowance.
According to CitationDuke (2008), the FDA Poisonous Plant Database lists five titles alluding to the toxicity of L. aestuans. Once other studies have validated its safety as a nutritional supplement, L. aestuans could be used in projects to fight malnutrition in poor communities because it is a ruderal species that is easily found in northeastern Brazil. It is likely that the toxicity of this species is only in the hairs of the stems, which are deciduous, sting and burn the skin upon contact and bring about a sensation of heat and a particular itchiness, followed by numbness and irritation. The heating process recommended by specialists causes the disintegration of these hairs and allows the dietary use of the plant.
X. sagittifolium is a leafy plant utilized as food in some Brazilian states (Pinto et al., Citation1999) and other countries (CitationSefa-Dedeh & Agyir-Sackey, 2004), yet no data on the Ca++ content of its cooked leaves were found; this information is important because it is directly related to the way the species is used as food. The amount of free calcium (Ca++) found in the X. sagittifolium leaves analyzed was interesting, taking into consideration the recommended daily intake of this mineral. In fresh leaves, the concentration was 273.17 mg/100 g, whereas the concentration in the cooked leaves was 369.81 mg/100 g. It is likely that some of the substances found in X. sagittifolium are soluble in water and promote calcium release, which may explain the higher Ca++ value for the cooked leaves. These results support the indication for this species, both as a dietary supplement and as a medicinal plant, in the prevention and treatment of osteoporosis.
A previous study on X. sagittifolium found that 35.87 g of leaf blades with venules, 36.18 g of leaf blades without venules or 51.95 g of petioles can supply the daily needs of individuals (Pinto et al. Citation1999). These authors showed that the fresh leaf blades and petioles are good sources of minerals and can be used as dietary supplements. However, our study showed that there is a 35% increase in the Ca++ in the cooked leaves of X. sagittifolium, and the difference found between the two studies may be due to different cultivation conditions or inherent genetic factors (CitationAgbor-Egbe & Richard, 1990; CitationSefa-Dedeh & Agyir-Sackey, 2004).
The presence of oxalates is one major limiting factor in the utilization of plants as foods or medicines. It is known that oxalate can bind calcium in a crystalline form that reduces the availability of the bound calcium for nutritional absorption in humans (CitationNakata & McConn, 2007). The calcium oxalates in X. sagittifolium make it toxic and have anti-nutritional properties (CitationSefa-Dedeh & Agyir-Sackey, 2004). CitationIwuoha and Kalu (1995) reported that the amount of oxalate diminishes with cooking, and boiling makes all of the deleterious effects disappear in one hour. In our study, the water in which the X. sagittifolium leaves were cooked was analyzed by optical microscopy, and it showed numerous raphides and druses. However, the mechanism of the decrease of the amount of oxalate by heat has not been fully determined (CitationSefa-Dedeh & Agyir-Sackey, 2004).
Conclusion
The information provided by the specialists at CESAM on the use of L. aestuans and X. sagittifolium for the prevention and treatment of bone diseases, such as osteoporosis, is in agreement with the results of the free calcium (Ca++) analyses carried out with the leaves of both species. However, before these species can be used medicinally, further studies are required to determine the bioavailability of the mineral, whether the calcium content is sufficient as a medical treatment and the toxicity of the plants.
Acknowledgements
We are indebted to the members of the Popular Health Center (CESAM) for their receptiveness and information provided and to the Conselho Nacional de Desenvolvimento Cientígico e Tecnológico (CNPq) for the Master’s scholarship granted to the first author.
Declaration of interest: The authors report no conflicts of interest and are responsible for the content and authorship of this paper.
References
- Agbor-Egbe T, Richard JE. (1990). Evaluation of the chemical composition of fresh and stored edible aroids. J Sci Food Agri, 53, 487–495.
- Alamu S, McDavid CR. (1978). Production of flowering in edible aroids by gibberellic acid. Trop Agric, 55, 81–86.
- Babalola OO, Akinsoyinu AO. (2009). Proximate composition and mineral profile of snail meat from different breeds of land snail in Nigeria. Pak J Nut, 8, 1842–1844
- Bradbury JH, Nixon RW. (1998). The acridity of raphides from the edible aroids. J Sci Food Agri, 608, 608–616.
- Fink S. (1991). The micromorphological distribution of bound calcium in needles of Norway spruce Picea abies (L.) Karst. New Phytol, 119, 33–40.
- Duke JA. (2008). Duke’s Handbook of Medicinal Plants of Latin America. Boca Raton: CRC Press, Taylor and Francis Group.
- Giacometti DC, León J. (1994). Tannia, Yautia (Xanthosoma sagittifolium) In: Hernándo Bermejo, J.E., León, J.E Eds Neglected Crops: 1492 from a Different Perspective. FAO Plant Prod Protec Series, 26, 253–##258.
- Iwuoha CI, Kalu FA. (1995). Calcium oxalate and physico-chemical properties of cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) tuber flours as affected by processing. Food Chem, 54, 61–66.
- Jiofack T, Fokunang C, Guedje N, Kemeuze V. 2009. Ethnobotanical uses of some plants of two ethnoecological regions of Cameroon. Afr J Pharm Pharacol, 3, 664–684.
- Lans CA. (2006). Ethnomedicines used in Trinidad and Tobago for urinary problems and diabetes mellitus. J Ethnobiol Ethnomed, 2, 45.
- Lans C. (2007). Ethnomedicines used in Trinidad and Tobago for reproductive problems. J Ethno Ethnomed, 3, 13.
- Nakata PA, McConn MM. (2007). Calcium oxalate content affects the nutritional availability of calcium from Medicago truncatula leaves. Plant Sci, 172, 958–961.
- National Research Council. (1981). Energy for Rural Development Renewable Resources and Alternative Technologies for Developing Countries. Washington: Academy Press.
- Occhiuto F, De Pasquale R, Guglielmo G, Palumbo DR. (2006). Effects of phytoestrogenic isoflavones from red clover (Trifolium pratense L.) on experimental osteoporosis. Phytother Res, 21, 30–134.
- Otchoumou A, N’Da K, Kouassi KD. (2005). L’élevage des escargots géants comestibles d’Afrique: Inventaire de végétaux sauvages consommés par Achatina achatina (Linné 1758) et préférences alimentaires. Livest Res Rural Develop Vol. 17, Art. #28. Retrieved May 18, 2011, from http://www.lrrd.org/lrrd17/10/otch17118.htm.
- Pinto NAVD, Vilas Boas BM, Carvalho VD. 1999. Caracterização mineral das folhas de taioba (Xanthosoma sagittifolium Schott). Ci Agrotec, 23, 57–61.
- Putnam SE, Scutt AM, Bicknell K, Priestley CM, Williamson EM. (2007). Natural products as alternative treatments for metabolic bone disorders and for maintenance of bone health. Phytother Res, 21, 99–112.
- Sefa-Dedeh S, Agyir-Sackey EK. (2004). Chemical composition and the effect of processing on oxalate content of cocoyam Xanthosoma sagittifolium and Colocasia esculenta cormels. Food Chem, 85, 479–487.