Sains Malaysiana 50(9)(2021): 2641-2651

http://doi.org/10.17576/jsm-2021-5009-12

 

Antimicrobial and Antioxidant Potential of Methanolic Extracts from Different Parts of Stevia rebaudiana Bertoni Cultivated in Bulgaria

(Potensi Antimikrob dan Antioksidan Ekstrak Metanol daripada Bahagian Berbeza Stevia rebaudiana Bertoni Ditanam in Bulgaria)

 

TONCHO DINEV1*, MILENA TZANOVA1, NIKOLINA RUSENOVA2, NELI GROZEVA3, MARIYA GERDZHIKOVA4 & GEORGI BEEV1

 

1Department of Biochemistry, Microbiology and Physics, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

 

2Department of Veterinary Microbiology, Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria

 

3Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

 

4Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

 

Diserahkan: 13 Oktober 2020/Diterima: 30 Januari 2021

 

ABSTRACT

Stevia rebaudiana Bertoni is a plant species which is frequently used not only as a sweetener, but also for its antibacterial and antioxidant properties. Nowadays, there are a large number of studies on the antimicrobial and antioxidant activity of S. rebaudiana leaves, but there are almost no data about the antimicrobial and antioxidant potential of extracts from the other parts of S. rebaudiana. The aim of the present study is to provide data of the antibacterial and antioxidant potential of methanolic extracts from different parts of S. rebaudiana (flowers, leaves, stems, rhizomes, and tubers) cultivated in Bulgaria. Antibacterial activity of the extracts against Staphylococcus aureus, Bacillus cereus and Escherichia coli was evaluated by agar well diffusion method, rutin content - by HPLC method, total phenolic content and radical scavenging potential - by UV-Vis analysis. S. rebaudiana extracts demonstrated antibacterial activity mainly against S. aureus - flower extracts expressed the highest activity, followed by the leaf and stem extracts. Only flower and leaf extracts demonstrated very low antibacterial activity against B. cereus. S. rebaudiana extracts did not show any antibacterial activity against E. coli. Methanolic extracts of this plant are rich in antioxidants. The highest concentrations of rutin and total phenols were found in the rhizomes of the plants, followed by the leaves, tubers, flowers, and stems, which corresponded to the radical scavenging potential of the same plant part. Comparisons between Trolox equivalents and gallic acid equivalents in different parts of S. rebaudiana on one hand, and Trolox equivalents and rutin concentration on the other hand showed a positive dependence and high values of the Pearson correlation - 0.9612 and 0.9707, respectively. The most important part of S. rebaudiana with medicinal significance (the leaves) has both comparatively good antibacterial activity and high antioxidant content, although the flowers and rhizomes expressed higher antibacterial and antioxidant activity, respectively. The experimental results imply that the cultivation area and climatic conditions of Bulgaria are very suitable for cultivation of S. rebaudiana plants with high content of antioxidants.

 

Keywords: Antimicrobial; antioxidant; methanolic extracts; plant parts; Stevia rebaudiana

 

ABSTRAK

Stevia rebaudiana Bertoni adalah spesies tumbuhan yang sering digunakan bukan hanya sebagai pemanis, tetapi juga untuk sifat antibakteria dan antioksidannya. Pada masa kini, terdapat sebilangan besar kajian mengenai aktiviti antimikrob dan antioksidan daun S. rebaudiana, tetapi hampir tidak ada data mengenai potensi antimikrob dan antioksidan ekstrak daripada bahagian lain S. rebaudiana. Tujuan kajian ini adalah untuk menyediakan data potensi antibakteria dan antioksidan ekstrak metanol daripada pelbagai bahagian S. rebaudiana (bunga, daun, batang, rizom dan tuber) yang ditanam di Bulgaria. Aktiviti antibakteria ekstrak terhadap Staphylococcus aureus, Bacillus cereus dan Escherichia coli dinilai dengan kaedah penyebaran agar baik, kandungan rutin - dengan kaedah HPLC, jumlah kandungan fenol dan potensi penyingkiran radikal - dengan analisis UV-Vis. Ekstrak S. rebaudiana menunjukkan aktiviti antibakteria terutamanya terhadap S. aureus - ekstrak bunga menunjukkan aktiviti tertinggi, diikuti oleh ekstrak daun dan batang. Hanya ekstrak bunga dan daun menunjukkan aktiviti antibakteria yang sangat rendah terhadap B. cereus. Ekstrak S. rebaudiana tidak menunjukkan aktiviti antibakteria terhadap E. coli. Ekstrak metanol tumbuhan ini kaya dengan antioksidan. Kepekatan tertinggi rutin dan fenol total terdapat pada rizom tanaman, diikuti oleh daun, tuber, bunga dan batang, yang sesuai dengan potensi radikal pencucian pada bahagian tanaman yang sama. Perbandingan antara setara Trolox dan setara asid galik di bahagian yang berlainan di S. rebaudiana di satu pihak, dan setara Trolox dan kepekatan rutin di sisi lain menunjukkan pergantungan positif dan nilai tinggi korelasi Pearson - masing-masing 0,9612 dan 0,9707. Bahagian S. rebaudiana yang paling penting untuk kepentingan perubatan (daun) mempunyai aktiviti antibakteria yang cukup baik dan kandungan antioksidan yang tinggi, walaupun bunga dan rizom masing-masing menunjukkan aktiviti antibakteria dan antioksidan yang lebih tinggi. Hasil uji kaji menunjukkan bahawa kawasan penanaman dan keadaan iklim Bulgaria sangat sesuai untuk penanaman tanaman S. rebaudiana dengan kandungan antioksidan yang tinggi.

 

Kata kunci: Antimikrob; antioksidan; bahagian tanaman; ekstrak metanol; Stevia rebaudiana

 

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