Aktivitas antioksidan ekstrak metanolik daun beluntas (Pluchea indica Less) dan fraksinya serta kemampuan mencegah warmed over flavor pada daging itik yang telah dipanaskan

Abstract

Pluchea indica Less is a herb commonly used as food and traditional medicine. Its leaves have antioxidant activity due to its various phytochemical compounds. The antioxidant activity of methanolic extract of Pluchea leaves to prevent cooked duck meat warmed over flavor (WOF) is still under explored. The objective of this study was to investigate the antioxidant activity of methanolic extract of Pluchea leaves and its fraction (ethyl acetate, water, and n-butanol) by using different analysis approaches test systems (2,2-phenyl-1-picrylhydrazyl (DPPH), superoxide and hydroxyl radical-scavenging activities, hydrogen peroxide scavenging activity, ferric reducing power, iron chelating capacity, and -carotene-linoleic acid bleaching assay). Furthermore, their application as inhibitor to cooked duck meat WOF has also been conducted. Antioxidant activity of Pluchea leaves was obtained by dividing its leaves into 3 groups, i.e 1-3, 4-6 and >6. The methanolic extract of those groups contained phytochemical compounds, such as tannin, sterol, phenol hydroquinone, and flavonoid. The methanolic extract of 1-6 Pluchea leaves (EMB) had more potential source of DPPH free radical scavenging activity. In addition, this extract was fractionated by various solvents with different polarity, such as ethyl acetate, n-butanol, and water. The result showed that ethyl acetate fraction (FEA) had higher antioxidant activity than EMB and the other fraction, but its activity was lower than methanolic extract of green tea (EMT). The antioxidant activity assay of EMB and FEA was compared to BHT and -tocopherol by using different analysis approaches test systems. It showed that FEA had superoxide radical-scavenging activity, iron chelating capacity and ferric reducing power, while EMB had superoxide radical-scavenging activity, ferric reducing power and -carotene–linoleic acid bleaching assay. FEA at 250 ppm concentration was more effective to prevent the formation of cooked duck meat WOF than FEA at 600 ppm concentration and EMB. This fraction significantly inhibited the oxidation of PUFA (linoleic and arachidonic acids) and the formation of malondialdehide (MDA) and hexanal content. In comparison with FEA, EMB showed less potent antioxidant activity. However, the volatile compounds in EMB extract had an effect in improving sensory properties of duck meat, mainly by increased hedonic-preference scores on acceptance sensory test and also suppressed green and grassy aromatic intensities of duck meat during cooking and storage.

Beluntas (Pluchea indica Less) merupakan famili Asteraceae yang telah dimanfaatkan masyarakat sebagai pangan dan sediaan obat bahan alam. Senyawaan fitokimia yang terkandung dalam daun beluntas mempunyai aktivitas antioksidan. Ekstrak etanolik daun beluntas telah terbukti mampu menangkap radikal bebas 1,1-difenil-2- pikrilhidrasil (DPPH) dan asam 2,2'-azino-bis-(3-etil bensotiasolin-6-sulfonat) (ABTS), mereduksi ion besi, dan menghambat pembentukan malondialdehida (MDA). Penelitian sebelumnya menginformasikan bahwa metanol merupakan pelarut yang efektif untuk mengekstrak senyawa fenolik tanaman sehingga diperoleh aktivitas antioksidan tinggi. Sejauh ini ekstrak metanolik daun beluntas (EMB) dan fraksinya belum diketahui aktivitas antioksidannya serta kemampuannya mencegah warmed over flavor (WOF) pada daging itik yang telah dipanaskan. Penggunaan daging itik pada penelitian ini disebabkan komoditas tersebut mudah mengalami penurunan kualitas selama pemanasan dan penyimpanan karena reaksi oksidasi. Salah satu indikasi kerusakan akibat reaksi oksidasi adalah munculnya WOF. Penelitian ini secara garis besar difokuskan pada 3 tahapan, yaitu: 1) tahap seleksi daun beluntas yang berpotensi sebagai sumber antioksidan alami; 2) tahap pengujian aktivitas antioksidan ekstrak metanolik daun beluntas dan fraksinya yang berpotensi sebagai antioksidan alami secara in vitro, meliputi kemampuan menangkap spesies oksigen reaktif (SOR) (hidrogen peroksida, radikal superoksida dan hidroksil), mereduksi dan mengkelat ion besi, dan menghambat oksidasi asam linoleat--karoten; dan 3) tahap pengujian aktivitas antioksidan EMB dan fraksinya yang paling berpotensi sebagai antioksidan alami dalam mencegah WOF daging itik.