Abstract
Melastoma malabathricum (MM) is a well-known plant in Malaysian traditional medicine, locally known as senduduk. Its ethanol and aqueous extracts have been used in the present investigation to study the immunomodulatory role on human peripheral blood mononuclear cell (PBMC), and the DPPH, ABTS and FRAP free radical scavenging activities were also measured. Total flavonoids and total phenolic contents were assayed and the antibacterial effect was tested against four species of bacteria; two Gram-positive (Staphylococcus aureus and Streptococcus agalactiae) and two Gram-negative (Escherichia coli and Klebsilla pneumonia). The tests were carried out using the disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Moreover, the acute toxicity was evaluated in vivo on the ethanol extract of MM to establish its safety when administered orally. In our results, both extracts of MM showed abilities to scavenge DPPH and ABTS free radicals, IC50 values: (11.599 ± 0.84, 10.573 ± 0.58 µmol/L) and (62.657 ± 0.78, 63.939 ± 0.48 µmol/L) for ethanol and aqueous extracts respectively. Indeed the ethanol extract evidenced high phenolic content (384.33 ± 0.005 mg/g), flavonoids contents (85.8 ± 0.009 mg/g) and ferric reducing antioxidant power (33,590 ± 0.038 mmol/g), with high activity against S. aureus and S. agalactiae (11 ± 0.3 and 12 ± 0.6 mm inhibition zones). Likewise, the percentage of peripheral blood mononuclear cells (PBMC) viability was increased in response to MM, IC50 values (1.781 ± 1.2 and 6.545 ± 0.93 µg/mL) for ethanol and aqueous extracts, respectively. In addition, our results showed that the MM extract is safe even at a high dose of 5,000 mg/kg and has no oral toxicity. These findings suggest the excellent medicinal bioactivity of MM and explain the popularity of this plant in the folk medicine as a remedy for different illnesses.
Highlights
Plants derived natural products are the source of most active components of medications, which in turn play a significant role in the treatment or prevention of human illnesses
Polyphenols are the largest group of antioxidants that have the ability to up-regulate some metal chelating reactions and scavenge free radicals, like singlet oxygen and hydrogen peroxide which should be regularly removed from cells to maintain their normal functions [15]
Phytochemical screening of MM revealed that the ethanol extract showed higher total phenolics (384.33 ± 0.005 mg/g) and flavonoids contents (85.8 ± 0.009 mg/g). These results revealed that the free radical scavenging activity might not be related to the presence of phenols components, These findings support the previous research of [18] who reported that Cassia tora extract possesses potent antiradical and antioxidant which is not correlated with the total phenols content of the same plant
Summary
Plants derived natural products are the source of most active components of medications, which in turn play a significant role in the treatment or prevention of human illnesses. Melastoma malabathricum (MM) is a plant from the family (Melastomataceae) found in many regions of tropical Asia where it is known by different local names such as the Straits Rhododendron (Singapore), Malabar melastome (Australia), Indian-rhododendron or Lutki (India) and Senduduk (Malaysia). It has been used in the traditional medicine to treat diarrhea, accelerate wound healing, lowering high blood pressure, treat diabetes, prevent scarring of smallpox and to treat piles [2,3]. Melastoma malabathricum’s oral acute toxicity on Sprague Dawley rats in vivo and scavenging activity toward DPPH, ABTS and FRAP free radicals, phytochemical screening of total phenolic and flavonoids contents, antibacterial effects against Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli and Klebsilla pneumonia and immunomodulatory role on human peripheral blood mononuclear cell (PBMC) in vitro
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