Optimasi Metode Microwave-Assisted Extraction terhadap Polifenol dan Aktivitas Biologis Tanaman Krokot (Portulaca oleracea L.)

Abstract

Indonesia memiliki potensi tanaman obat yang berlimpah dan kaya akan senyawa bioaktif. Salah satu tanaman yang potensial adalah krokot (Portulaca oleracea L.), yang secara tradisional digunakan untuk mengatasi berbagai gangguan kesehatan dan diketahui mengandung senyawa fenolik dan flavonoid dengan potensi aktivitas biologis, seperti antioksidan, antidiabetes, dan antihiperpigmentasi. Namun, belum tersedia metode ekstraksi terstandar yang mampu mengoptimalkan perolehan senyawa bioaktif tersebut. Penelitian ini bertujuan untuk mengoptimalkan proses ekstraksi menggunakan metode microwave-assisted extraction (MAE) dengan pendekatan response surface methodology (RSM), serta mengevaluasi aktivitas penghambatan enzim a-glukosidase dan tirosinase oleh ekstrak hasil optimasi dibandingkan dengan ekstrak metode konvensional. Penelitian terdiri atas dua tahap. Tahap pertama bertujuan mengoptimalkan proses ekstraksi senyawa polifenol dari tanaman krokot menggunakan metode MAE dengan pendekatan RSM tipe central composite design (CCD). Tiga variabel bebas yang dikaji meliputi konsentrasi metanol, rasio pelarut terhadap bahan, dan waktu ekstraksi. Enam parameter respons diamati, yaitu kandungan fenolik total (TPC), flavonoid total (TFC), serta kapasitas antioksidan berdasarkan metode CUPRAC, FRAP, ABTS, dan DPPH. Hasil analisis menunjukkan bahwa seluruh model respons valid dan akurat, dengan nilai residual standard error (RSE) < 10%. Dua formula optimum berhasil diperoleh, masing-masing mewakili karakteristik antioksidan berbasis reducing power dan radical scavenging dengan nilai desirability mendekati satu. Tahap kedua penelitian bertujuan mengevaluasi dan membandingkan aktivitas penghambatan enzim a-glukosidase dan tirosinase dari ekstrak hasil optimasi dengan ekstrak metode konvensional. Ekstrak MAE-optimum menunjukkan aktivitas inhibisi enzim yang lebih tinggi dibandingkan ekstrak infusa dan maserasi. Hasil ini menunjukkan bahwa ekstrak yang dihasilkan melalui proses optimasi memiliki potensi sebagai inhibitor alami yang kuat. Analisis lebih lanjut menggunakan instrumen LC-HR/MS berhasil mengidentifikasi sejumlah metabolit sekunder yang berkontribusi terhadap aktivitas biologis, termasuk gentisic acid 5-O-ß-d-xyloside, salicylic acid, p-coumaric acid, kaempferol, dan apigenin. Senyawa-senyawa ini diketahui memiliki aktivitas sebagai antioksidan serta sebagai inhibitor enzim a-glukosidase dan tirosinase yang mendukung efektivitas biologis ekstrak krokot secara komprehensif. Penelitian ini secara keseluruhan menunjukkan bahwa pendekatan integratif antara metode MAE dan optimasi RSM-CCD efektif untuk menghasilkan ekstrak krokot dengan kandungan polifenol dan potensi biologis yang tinggi. Temuan ini mendukung pengembangan ekstrak krokot sebagai kandidat bahan aktif alami untuk aplikasi fitofarmaka dan kosmetik, serta memberikan kontribusi terhadap inovasi metode ekstraksi tanaman obat secara efisien.

Indonesia possesses abundant medicinal plant resources rich in bioactive compounds. One such promising plant is Portulaca oleracea L. (purslane), which has been traditionally used to treat various health conditions and is known to contain phenolic and flavonoid compounds with potential biological activities, including antioxidant, antidiabetic, and anti-hyperpigmentation properties. However, a standardized extraction method that effectively optimizes the recovery of these bioactive compounds has yet to be established. This study aims to optimize the extraction process using microwave-assisted extraction (MAE) combined with response surface methodology (RSM), and to evaluate the inhibitory activity of the optimized extract on a-glucosidase and tyrosinase enzymes compared to extracts obtained through conventional methods. The research was conducted in two stages. The first stage focused on optimizing the extraction of polyphenolic compounds from P. oleracea using MAE with a central composite design (CCD)-based RSM approach. Three independent variables were investigated: methanol concentration, solvent-to-material ratio, and extraction time. Six response parameters were measured, including total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity assessed by CUPRAC, FRAP, ABTS, and DPPH assays. The analysis demonstrated that all response models were valid and accurate, with residual standard error (RSE) values below 10%. Two optimum extraction formulas were obtained, representing antioxidant characteristics based on reducing power and radical scavenging, each with desirability values approaching one. The second stage aimed to evaluate and compare the inhibitory activities of the optimized extracts and conventionally prepared extracts against a-glucosidase and tyrosinase enzymes. The MAE-optimized extract exhibited higher inhibitory activity than the infusion and maceration extracts, indicating its strong potential as a natural enzyme inhibitor. Further analysis using LC-HR/MS identified several secondary metabolites contributing to the observed biological activities, including gentisic acid 5-O-ß-d-xyloside, salicylic acid, p-coumaric acid, kaempferol, and apigenin. These compounds are known for their antioxidant properties as well as their roles as inhibitors of a-glucosidase and tyrosinase, thus supporting the comprehensive biological efficacy of the optimized purslane extract. Overall, this study demonstrates that the integrative approach combining MAE and RSM-CCD is effective in producing purslane extracts with high polyphenol content and strong biological potential. These findings support the development of purslane extract as a promising natural active ingredient for fitopharmaceutical and cosmetic applications, and contribute to innovation in efficient medicinal plant extraction methods.