Comparison of leaf morphology and anatomy among Malva sylvestris ("gerânio-aromático"), Pelargonium graveolens ("falsa-malva") and Pelargonium odoratissimum ("gerânio-de-cheiro")

91 Comparison of leaf morphology and anatomy among Malva sylvestris (“gerânioaromático”), Pelargonium graveolens (“falsa-malva”) and Pelargonium odoratissimum (“gerânio-de-cheiro”) ROMITELLI, I.* & MARTINS, M.B.G. Universidade Estadual Paulista, Campus do Litoral Paulista, Unidade São Vicente, CEP: 11330-900, São Vicente, Brasil, * RESUMO: Comparação da Morfologia e da anatomia foliar entre as espécies Malva sylvestris (gerânio-aromático), Pelargonium graveolens (falsa-malva) e Pelargonium odoratissimum (gerânio-de-cheiro). Malva sylvestris é comumente confundida com Pelargonium graveolens e Pelargonium odoratissimum devido às semelhanças na morfologia foliar. As folhas de M. sylvestris possuem antocianinas com propriedades citotóxicas, antiinflamatória, antitumoral e antioxidante já comprovadas cientificamente. As folhas de P. odoratissimum apresentam óleo essencial com propriedades antibacteriana e espasmolítica, e o óleo essencial da folha de P. graveolens possui atividade antimicrobiana e antifúngica. O objetivo deste estudo foi analisar morfo-anatomicamente as folhas destas espécies, apontando diferenças que possam ser utilizadas para esclarecer controvérsias na sua utilização como planta medicinal. Com a finalidade de se comparar anatomicamente a estrutura de cada planta, as amostras foram observadas por Microscopia de Luz e Microscopia Eletrônica de Varredura (MEV). A anatomia foliar entre as espécies foi bem distinta. Malva sylvestris apresentou tricomas do tipo capitado, estrelado e tector, além de drusas e células mucilaginosas. A distinção entre P. graveolens e P. odoratissimum foi observada em relação aos tricomas. Ambas as espécies apresentaram tricomas glandulares e tectores, sendo que P. graveolens se diferencia pela maior altura dos tricomas tectores e menor quantidade destes em relação ao P. odoratissimum. Este trabalho permitiu constatar diferenças anatômicas, auxiliando na taxonomia e classificação entre estas espécies. Palavras-chaves: anatomia foliar, Malva sylvestris, Pelargonium graveolens, Pelargonium odoratissimum, plantas medicinais. Abstract: Malva sylvestris is generally confused with Pelargonium graveolens and Pelargonium odoratissimum due to similarities in their leaf morphology. The leaves of M. sylvestris have anthocyanins with scientifically proven cytotoxic, anti-inflammatory, antitumor and antioxidant properties. The leaves of P. odoratissimum have essential oil with antibacterial and spasmolytic properties, while the essential oil from P. graveolens has antimicrobial and antifungal activity. The aim of this study was to morpho-anatomically analyze the leaves of these species, indicating differences that can be used to clarify controversies about their use as medicinal plants. To anatomically compare the structure of each plant, samples were observed by Light Microscopy and Scanning Electron Microscopy (SEM). Leaf anatomy among species was quite different. Malva sylvestris showed capitate starry tector trichomes, as well as druses and mucilaginous cells. P. graveolens and P. odoratissimum differed as to trichomes. Both species had tector and glandular trichomes, and P. graveolens is distinguished for the greater height of tector trichomes and less quantity of the latter relative to P. odoratissimum. This study allowed the detection of anatomical differences, assisting in the taxonomy and classification of these species. Key words: leaf anatomy, Malva sylvestris, Pelargonium graveolens, Pelargonium odoratissimum, medicinal plants. Recebido para publicação em 07/12/2011 Aceito para publicação em 01/08/2012 Rev. Bras. Pl. Med., Botucatu, v.15, n.1, p.91-97, 2013. 92 INTRODUCTION The use of medicinal plants by a traditional community, both in the simplest forms such as tea and in the sophisticated manufacturing industry, transforming them into tablets, drops or capsules with the isolated active principle, is motivated by properties to generate beneficial reactions to the body (Lorenzi, 2008). However, any use requires caution, especially the species identification since they are difficult to distinguish when dehydrated. Recently, considering the dental industry, research has shown the promising use of medicinal plants: in vitro studies with hydroalcoholic extract from Myracrodruon urundeuva, Psidium guajava and Malva sylvestris showed potential antimicrobial activity against the biofilm former microorganisms, but also antifungal activity on Candida strains isolated from the oral cavity (Alves, 2009). Malva sylvestris belongs to the family Malvaceae, is native to Europe and is cultivated in southern Brazil. The pharmacological properties of Malva sylvestris are concentrated in its leaves. Among them is antimicrobial activity, proven by numerous studies involving tests with ethanolic extracts against Staphylococcus aureus (Wang et al., 2006; Quave, 2008), Bacillus subtilis, Pseudomonas albuginea, Escherichia coli, Saccharomyces cerevisiae (Souza et al., 2004), Streptococcus mutans and Streptococcus sobrinus (Alves, 2009). The action of its leaves also include stimulation of phagocytes (Delaveau et al., 1980), muscle relaxation, uterine stimulation (Calegari, 1942), nociception (Esteves, 2009), cytotoxic activity (Alesiani, 2007) and topical anti-inflammatory action on the skin (Chiclana, 2009). The large number of pharmacological properties of M. sylvestris is justified by the complexity of its composition, which consists of tetrahydroxilatated sesquiterpenes and diterpenes, two monoterpenes, six normal-C13 terpenes and eleven aromatic compounds (Cutillo, 2006). Similarly to the anthocyanin in the leaves, which has a natural potential for degrading free radicals, it serves as antioxidant, reducing total cholesterol, triglycerides in the blood and preventing thrombosis and cardiocerebral angiopathy (Wang, 2005). The genus Pelargonium (Geraniaceae), according to a review by Knuth (1912), comprises about 250 species, of which 80% occur in southern Africa and the rest in eastern Africa, Madagascar and Australia. In their chemical constitution, Pelargonium graveolens and Pelargonium odoratissimum have flavonoids such as quercetin, kaempferol and myricetin, and P. graveolens is highlighted for its greater concentration of the first two compounds and proanthocyanidins (Williams et al., 2001). Essential oils are also in their chemical composition, and in P. graveolens the most important oils are citronellol and geraniol (Shin & Lim, 2004). After the experiment of Choi et al. (2007), citronellol acted against the resistant strains of Streptococcus pneumonia, reducing the concentration of administered antibiotics and the side effects. P. graveolens essential oil, in synergy with the antibiotic ketoconazole, may also be recommended as a new herbal antimicrobial because of its strong action against Trichophyton soudanense and Tricchophyton schoenleinii, reinforcing another case of reduction in synthetic antibiotic use (Shin & Lim, 2004). The a (...truncated)