Sains Malaysiana 47(4)(2018): 731-739

http://dx.doi.org/10.17576/jsm-2018-4704-11

Effect of Tea Polyphenols on α-Amylase Activity in Starch Hydrolysis

(Kesan Polifenol Teh terhadap Aktiviti α-Amilase pada Hidrolisis Kanji)

NURUL NADIAH BINTI ISMAIL, UTHUMPORN UTRA*, CHENG LAI HOONG & AZHAR BIN MAT ESA

Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia

Diserahkan: 13 Jun 2017/Diterima: 26 Oktober 2017

ABSTRACT

Tea leaves (Camellia sinensis) contain bioactive compounds that can help prevent certain diseases. In this study, the inhibitory effect of polyphenolic components of different types of tea leaves (green, oolong and black) extracted using different solvents (ethanol, methanol and water) on α-amylase activity of human saliva were investigated in vitro. Total phenolic content (TPC), total flavonoid content (TFC), ferric reducing/antioxidant power and inhibition of free radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl of the extracts were measured. Content of gallic acid, caffeine and four catechins also were quantified by high performance liquid chromatography. The ethanol extracts had the highest TPC (124.34-231.23 mg gallic acid equivalents (GAE)/g sample), followed by the methanol extracts (124.28-209.76 mg GAE/g sample) and the water extracts (66.89-136.51 mg GAE/g sample). All three solvent extractions of green tea leaves contained the highest TPC, TFC and antioxidant activity, followed by oolong and black tea leaves. Green tea leaves contained higher amounts of catechins than oolong and black tea leaves. All four catechins were detected in green and oolong tea leaves but only gallocatechin gallate was found in black tea leaves. Next, the effect of tea leaves extracts on starch hydrolysis by α-amylase enzyme from human saliva at 37°C was studied. The starches were hydrolyzed with 0.01% enzyme for 240 min and the extent of hydrolysis was determined based on the dextrose equivalent value. The extent of starch hydrolysis by the tea leaves was as follows: green tea > oolong tea > black tea. The low degree of hydrolysis for black tea was due to its strong inhibitory effect on α-amylase activity. Thus, green, oolong and black tea leaves inhibit activity of α-amylase to different degrees due to their differing compositions and structures of phenolic compounds.

Keywords: α-amylase activity; black tea; green tea; hydrolyzing starch; oolong tea; phenolic content

ABSTRAK

Daun teh (Camellia sinensis) mempunyai sebatian bioaktif sebagai pencegahan penyakit tertentu. Penyelidikan ini mengkaji tentang kesan perencatan enzim α-amylase oleh komponen polifenol daripada pelbagai jenis daun teh (hijau, oolong dan hitam) dengan menggunakan kaedah pengekstrakan (etanol, metanol dan air) yang berlainan secara in vitro. Dalam kajian ini, penentuan jumlah kandungan fenolik (TPC), jumlah kandungan flavonoid (TFC), pengurangan kuasa ferum antioksidan (FRAP) dan perencatan aktiviti pembasmian radikal bebas oleh 1,1-difenil-2-picrilhidrazil (DPPH) dijalankan. Kandungan asid gallik, kafein dan empat jenis catechin telah dianalisis dan diukur dengan menggunakan alat analisis kromatografi cecair prestasi tinggi (HPLC). Pengekstrakan etanol menghasilkan jumlah kandungan fenolik tertinggi (124.34-231.23 mg GAE/g sampel), diikuti dengan pengekstrakan metanol (124.28-209.76 mg GAE/g sampel) dan pengekstrakan menggunakan air (66.89-136.51 mg GAE/g sampel). Ketiga-tiga jenis larutan pengekstrakan menunjukkan daun teh hijau mempunyai kandungan TPC, TFC dan antioksidan tertinggi diikuti oleh daun teh oolong dan daun teh hitam. Daun teh hijau mengandungi jumlah katekin lebih tinggi daripada daun teh oolong dan daun teh hitam. Keempat-empat katekin dijumpai terkandung dalam daun teh hijau dan teh oolong, tetapi hanya gallokatecin gallat sahaja dijumpai dalam teh hitam. Selain itu, kesan penambahan ekstrak daun teh pada hidrolisis kanji dengan menggunakan enzim α-amilase daripada air liur manusia pada suhu 37°C telah dikaji. Kanji telah dihidrolisiskan dengan menggunakan enzim berkepekatan 0.01% selama 240 min dan kadar hidrolisis ditentukan oleh nilai bersamaan dektrosa. Keputusan hidrolisis kanji ditunjukkan dalam urutan: teh hijau> teh oolong> teh hitam. Tahap hidrolisis terendah untuk teh hitam terbukti daripada perencatan tertinggi teh hitam pada aktiviti enzim α-amilase. Ini membuktikan bahawa penambahan daun teh yang berbeza menunjukkan tahap perencatan aktiviti enzim α-amilase yang berbeza kerana komposisi dan struktur sebatian fenolik yang berbeza pada setiap jenis daun teh.

Kata kunci: Aktiviti α-amylase; teh hitam; teh hijau; hidrolisis kanji; teh oolong; kandungan fenolik

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