Phytochemical composition and biological activities of extracts from ten species of the family Melastomataceae Juss / Composição fitoquímica e atividades biológicas de extratos de dez espécies da família Melastomataceae Juss

Plants possess a renewable source of metabolites with enormous chemical structural diversity, which may have potential therapeutic relevance. Furthermore, this chemical diversity favors the possibility of finding new and different chemical constituents with antimicrobial, antioxidant and anti-tumor activities. This work analyzed preliminary phytochemical profiles and evaluated the antimicrobial, antioxidant and cytotoxic activities of hexane extracts of leaves of ten species of the family Melastomataceae. Phytochemical screening was performed using staining methods while total phenols and flavonoids were quantified by spectrophotometry. Antimicrobial activity was evaluated using the disk diffusion method. Antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazil (DPPH) method. Toxicity was recorded using the lethality test with Artemia salina Leach (1819). Cytotoxic activity of the extracts was assessed in vitro with acute monocytic leukemia cells (THP-1). Phytochemical analysis detected the presence of tannins, terpenes, steroids, polyphenols and flavonoids and the absence of alkaloids. Clidemia capitellata (Bonpl.) D. Don had the greatest amount of polyphenols (205.95 mg/g ± 4.14) while Clidemia hirta (L.) D. Don had the highest content of total flavonoids (143.99 mg/g ± 4.18). The hexane extracts did not show antimicrobial activity nor toxicity against Artemia salina. The extract of Tibouchina francavillana Cogn. was the most active in sequestering the DPPH radical. The extracts showed cytotoxicity in THP-1 cells with the appearance of apoptotic bodies and cell death. The extracts of Miconia amoena, Clidemia sericea and Clidemia capitellata are non-toxic against Artemia salina and induce the formation of apoptotic bodies and cell death of the THP-1 lineage.

Os vegetais apresentam uma fonte renovável de metabólitos com enorme diversidade química estrutural, os quais podem apresentar potencial relevante na terapêutica, aumentando as possibilidades de encontrar novos e diferentes constituintes químicos com atividades antimicrobiana, antioxidante e antitumoral. Este trabalho analisou o perfil fitoquímico preliminar e as atividades antimicrobiana, antioxidante, citotóxica dos extratos em hexano das folhas de dez espécies da família Melastomataceae. A triagem fitoquímica foi executada utilizando métodos de coloração e quantificação de fenóis e flavonoides totais por espectrofotometria. A atividade antimicrobiana foi realizada pelo método de difusão em disco. A atividade antioxidante foi determinada pelo método 2,2-difenil1-picrilhidrazila (DPPH). A toxicidade foi registrada utilizando o ensaio de letalidade com Artemia salina Leach (1819). A atividade citotóxica dos extratos foi realizada in vitro com células leucêmicas monocítica aguda (THP-1). A análise fitoquímica detectou a presença de taninos, terpenos, esteroides, polifenóis, flavonoides e ausência de alcaloides. A maior quantificação de polifenóis foi da Clidemia capitellata (Bonpl.) D. Don (205,95 mg/g ± 4,14) e o extrato de Clidemia hirta (L.) D. Don apresentou maior teor de flavonoides totais (143,99 mg/g ± 4,18). Os extratos hexânicos não demostraram atividade antimicrobiana e nem toxicidade frente à Artemia salina. O extrato de Tibouchina francavillana Cogn. foi o mais ativo no sequestro do radical DPPH. Os extratos apresentaram citotoxicidade em células THP-1, com visualização de corpos apoptóticos e morte celular. Os extratos de Miconia amoena, Clidemia sericea e Clidemia capitellata são atóxicos contra Artemia salina e induzem a formação de corpos apoptóticos e morte celular da linhagem THP-1.

Antinociception of petroleum ether fraction derived from crude methanol extract of Melastoma malabathricum leaves and its possible mechanisms of action in animal models.

BACKGROUND: Melastoma malabathricum L. (family Melastomaceae) has been traditionally used as remedies against various ailments including those related to pain. The methanol extract of M. malabathricum leaves has been proven to show antinociceptive activity. Thus, the present study aimed to determine the most effective fraction among the petroleum ether- (PEMM), ethyl acetate- (EAMM) and aqueous- (AQMM) fractions obtained through successive fractionation of crude, dried methanol extract of M. malabathricum (MEMM) and to elucidate the possible mechanisms of antinociception involved. METHODS: The effectiveness of fractions (100, 250 and 500 mg/kg; orally) were determine using the acetic acid-induced abdominal constriction test and the most effective extract was further subjected to the hot plate- or formalin-induced paw licking-test to establish its antinociceptive profile. Further elucidation of the role of opioid and vanilloid receptors, glutamatergic system, and nitric oxide/cyclic guanosine phosphate (NO/cGMP) pathway was also performed using the appropriate nociceptive models while the phytoconstituents analyses were performed using the phytochemical screening test and, HPLC-ESI and GCMS analyses. RESULTS: PEMM, EAMM and AQMM significantly (p < 0.05) attenuated acetic acid-induced nociception with the recorded EC50 of 119.5, 125.9 and 352.6 mg/kg. Based on the EC50 value, PEMM was further studied and also exerted significant (p < 0.05) antinociception against the hot plate- and formalin-induced paw licking-test. With regards to the mechanisms of antinociception,: i) PEMM significantly (p < 0.05) attenuated the nociceptive action in capsaicin- and glutamate-induced paw licking test.; ii) naloxone (5 mg/kg), a non-selective opioid antagonist, failed to significantly (p < 0.05) inhibit PEMM's antinociception iii) L-arginine (a nitric oxide precursor), but not NG-nitro-L-arginine methyl esters (L-NAME; an inhibitor of NO synthase), methylene blue (MB; an inhibitor of cGMP), or their respective combination, significantly (p < 0.05) reversed the antinociception of PEMM. Phytochemical analyses revealed the presence of several antinociceptive-bearing bioactive compounds, such as triterpenes and volatile compounds like oleoamide and palmitic acid. The presence of low flavonoids, such as gallocatechin and epigallocatechin, saponins and tannins in PEMM might synergistically contribute to enhance the major compounds antinociceptive effect. CONCLUSION: PEMM exerted a non-opioid-mediated antinociceptive activity at the central and peripheral levels via the inhibition of vanilloid receptors and glutamatergic system, and the activation of NO-mediated/cGMP-independent pathway. Triterpenes, as well as volatile oleoamide and palmitic acid, might be responsible for the observed antinociceptive activity of PEMM.