Antioxidant - Antibacterial Activities and Phenolic / Flavonoid Content of Süpercritical CO2 Extract of Laurus nobilis L.

Abstract

Laurus nobilis L., commonly growing as a shrub or small tree, thrives in Mediterranean climates and is traditionally used for its aromatic leaves with antiseptic, antibacterial, and antioxidant properties. In this study, supercritical CO₂ extraction of L. nobilis leaves was performed under optimized conditions (300 MPa, 50 °C, 150 min) with ethanol added for homogenization. The extract was evaluated for antioxidant and antibacterial activities. Antibacterial activity was assessed against Gram-positive (Staphylococcus aureus ATCC 43300, Bacillus cereus ATCC 11778, Sarcina lutea ATCC 9341) and Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 70603, Salmonella enteritidis ATCC 13076) bacteria using the broth microdilution method. Antioxidant potential was determined via DPPH• scavenging, ABTS•⁺, CUPRAC, and metal chelating assays. The extract exhibited the strongest antibacterial effect against Gram-negative strains P. aeruginosa and K. pneumoniae (MIC: 1.562 mg/mL). Total phenolic and flavonoid contents were high, measured as 3291.62 ± 124.4 µg GAE/mg and 479.63 ± 28.7 µg QE/mg extract, respectively. In antioxidant assays, the extract showed notable ABTS•⁺ scavenging (IC₅₀: 30.26 ± 0.73 µg/mL), metal chelating activity (IC₅₀: 27.83 ± 0.71 µg/mL), and moderate CUPRAC reducing power (A₀.₅₀: 161.24 ± 0.29 µg/mL), while DPPH• scavenging activity was minimal. These results indicate that the extract possesses potent radical scavenging and metal-binding capacities, likely attributed to its rich phenolic composition. Overall, the findings support the ethnopharmacological use of L. nobilis and highlight its potential applications as a natural antioxidant and selective antimicrobial agent. The combination of high phenolic content, strong radical-scavenging, and selective antibacterial activity positions L. nobilis supercritical extracts as promising candidates for nutraceutical, pharmaceutical, and food industry applications.

Keywords

• laurus nobilis
• supercritical co2 extract
• antioxidant activity
• antibacterial activity
• phenolic compounds
• flavonoids

Laurus nobilis L.’nin Süperkritik CO₂ Ekstraktının Antioksidan – Antibakteriyel Aktiviteleri ile Fenolik / Flavonoid İçeriği

Abstract

Laurus nobilis L., Akdeniz ikliminde doğal olarak çalı veya küçük ağaç formunda yetişen, antiseptik, antibakteriyel ve antioksidan özellikleri nedeniyle geleneksel olarak kullanılan aromatik yapraklara sahip bir türdür. Bu çalışmada, L. nobilis yapraklarının süperkritik CO₂ ekstraksiyonu, optimize edilen koşullar altında (300 MPa, 50 °C, 150 dk) gerçekleştirilmiş ve homojenizasyon için etanol ilave edilmiştir. Elde edilen ekstraktın antioksidan ve antibakteriyel aktiviteleri değerlendirilmiştir. Antibakteriyel aktivite, Gram-pozitif (Staphylococcus aureus ATCC 43300, Bacillus cereus ATCC 11778, Sarcina lutea ATCC 9341) ve Gram-negatif (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 70603, Salmonella enteritidis ATCC 13076) bakterilere karşı mikrobros seyreltme (broth microdilution) yöntemi kullanılarak incelenmiştir. Antioksidan potansiyel ise DPPH•, ABTS•⁺, CUPRAC ve metal şelatlama testleri ile belirlenmiştir. Ekstrakt, en güçlü antibakteriyel etkiyi Gram-negatif P. aeruginosa ve K. pneumoniae suşlarına karşı göstermiştir (MIC: 1.562 mg/mL). Toplam fenolik ve flavonoid içerikleri sırasıyla 3291.62 ± 124.4 µg GAE/mg ve 479.63 ± 28.7 µg QE/mg ekstrakt olarak yüksek düzeyde bulunmuştur. Antioksidan test sonuçlarında ekstrakt; belirgin ABTS•⁺ giderimi (IC₅₀: 30.26 ± 0.73 µg/mL), güçlü metal şelatlama aktivitesi (IC₅₀: 27.83 ± 0.71 µg/mL) ve orta düzeyde CUPRAC indirgeme gücü (A₀.₅₀: 161.24 ± 0.29 µg/mL) göstermiştir. Buna karşın DPPH• radikal süpürücü aktivitesi oldukça düşük bulunmuştur. Bu sonuçlar, ekstraktın zengin fenolik bileşimiyle ilişkili olarak güçlü radikal süpürme ve metal bağlama kapasitesine sahip olduğunu göstermektedir. Genel olarak elde edilen bulgular, L. nobilis’in etnofarmakolojik kullanımını desteklemekte ve doğal antioksidan ile seçici antimikrobiyal ajan olarak potansiyelini ortaya koymaktadır. Yüksek fenolik içeriği, güçlü radikal giderici özellikleri ve seçici antibakteriyel aktivitesi sayesinde süperkritik CO₂ ile elde edilen L. nobilis ekstraktlarının nutrasötik, farmasötik ve gıda endüstrisi için umut vadeden adaylar olduğu sonucuna varılabilir.

Keywords

• Laurus nobilis
• süperkritik karbondioksit ekstraktı
• antioksidan aktivite
• antibakteriyel aktivite
• fenolik bileşikler
• flavonoidler

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