Abstract Melastoma malabathricum is one of the medicinal plants plated in West Kalimantan, Indonesia. Its leaves extraction using organic solvents revealed bioactive compounds and antioxidant activity. However, the antioxidant activity, toxicity, and chemical profile of water extract of M. malabathricum leaves are still unknown. This study aimed to determine extraction conditions that provide water extract of M. malabathricum with the highest antioxidant activity and the lowest toxicity. The extraction conditions were conducted at different water temperatures (25 ± 2 ºC and 90 ± 2 ºC), concentrations (10 and 5 g leaves/100 mL water), and extraction time (15, 30, and 45 minutes). Data analysis was performed by one-way ANOVA followed by Duncan's test (p < 0.05). The result showed that M. malabathricum leaves of 5g/100 mL extracted with hot water (90 ± 2 ºC) for 15 minutes showed the highest antioxidant activity (IC50 2.13 ± 19.20 ppm), which was higher than vitamin C (IC50 4.32 ± 0.16 ppm), and low toxicity (LC50 333.06 ± 99.45 ppm). Six compounds namely, 4-O-caffeoylquinic acid, quercimeritin, digiprolactone, 3-O-trans-coumaroylquinic acid, norbergenin, and arteamisinin were identified for the first time in the water extract of M. malabathricum leaves. These compounds, individually or extracted from other ingredients, have previously been reported to have antioxidant activity.

Abstract Apart from their nutritional value, vegetables and spices were empirically known to have functional properties such as antioxidant and antidiabetic activity. However, scientific evidence of these health effects is limited. In our effort to find potent raw material for antidiabetic functional food development, α-glucosidase inhibition and antioxidant activity of 15 Indonesian vegetables and spices methanolic extracts were screened. Their phytochemical profiles were assessed by determining total phenolic content (TPC) and 1H NMR fingerprinting. The results showed that the Syzygium polyanthum, Pluchea indica, Etlingera elaitor, and Cosmos caudatus had the highest GIA (IC50 11.76 ± 0.32, 12.17 ± 0.18, 53.13 ± 2.87, and 61.33 ± 1.21 μg/ml, respectively). The AA and TPC of the four samples were also higher than the others. The 1H NMR profiles of the active samples were different from the non-active samples mainly in the aromatic region. Further observation of the spectra revealed that caffeoylquinic derivatives and esculetin were identified in P. indica; while gallic acid, syringic acid, and myricetin were identified in S. polyanthum. These compounds were known to have antidiabetic activity through different mechanisms.

Resumo Frequentemente, alegam que arroz negro e arroz vermelho têm mais benefícios para a saúde que arroz branco. Tem sido relatado que eles têm maior atividade antioxidante e menor digestibilidade que arroz branco, propriedades funcionais que são importantes na prevenção de desordens metabólicas relacionadas com doenças, como diabete. Contudo, arroz cultivado em áreas diferentes ou submetido a processos diferentes tem apresentado propriedades físicas, químicas e funcionais diferentes. Portanto, o objetivo deste estudo foi determinar as propriedades físicas (dureza, cor e perfil de gelatinização) e químicas (composição centesimal, conteúdos totais de compostos fenólicos e flavonoides, e capacidade antioxidante) e a digestibilidade in vitro de arroz negro Solok (SBR), arroz vermelho Solok (SRR), arroz negro Tangerang (TBR), arroz vermelho Cianjur (CRR) e arroz branco Cianjur (CWR), cultivados em áreas diferentes da Indonésia. Os resultados demonstraram que as amostras de arroz cultivado em áreas diferentes apresentaram características físicas e composições químicas diferentes. A análise in vitro da digestibilidade do amido com α-amilase mostrou que o arroz pigmentado foi menos digestível (56,10% a 83,43%) que arroz branco (87,35%). Mostrou-se que o método de cozimento normal comumente usado pela sociedade reduziu, significativamente, os conteúdos totais de compostos fenólicos e flavonoides, e a capacidade antioxidante do arroz.

Abstract Black rice and red rice are often claimed to have more health benefits than white rice. They have been reported to have greater antioxidant activity and lower digestibility than white rice, functional properties which are important to prevent the metabolic disorders related to diseases such as diabetes. However, rice grown in different areas or subjected to different processing has shown different physical, chemical and functional properties. Thus the objectives of this study were to determine the physical properties (hardness, colour and gelatinization profile), chemical properties (proximate composition, total phenolic and flavonoid contents, antioxidant capacity), and the in vitro digestibility of Solok black rice (SBR), Solok red rice (SRR), Tangerang black rice (TBR), Cianjur red rice (CRR) and Cianjur white rice (CWR) cultivated in different areas in Indonesia. The results revealed that rice cultivated in different areas showed different physical characteristics and chemical compositions. The In vitro analysis of the digestibility of the starch with α-amylase showed that pigmented rice was less digestible (56.10% to 83.43%) than white rice (87.35%). A normal cooking method commonly used in society was found to significantly reduce the total phenolic content, flavonoids and antioxidant capacity of the rice.