Anti- Helicobacter pylori, Antioxidant, Antidiabetic, and Anti-Alzheimer's Activities of Laurel Leaf Extract Treated by Moist Heat and Molecular Docking of Its Flavonoid Constituent, Naringenin, against Acetylcholinesterase and Butyrylcholinesterase

Abstract

It is worth noting that laurel (Laurus nobilis L.) contains several pharmacologically and nutritionally active compounds that may differ according to the pretreatment process. The current study is designed to clarify the effect of moist heat on the phenolic and flavonoid constituents and anti-Helicobacter pylori, antioxidant, antidiabetic, and anti-Alzheimer's activities of laurel leaf extract (LLE). Unmoist-heated (UMH) and moist-heated (MH) LLEs showed the presence of numerous flavonoid and phenolic constituents, although at different levels of concentration. MH significantly induced (p < 0.05) the occurrence of most compounds at high concentrations of 5655.89 µg/mL, 3967.65 µg/mL, 224.80 µg/mL, 887.83 µg/mL, 2979.14 µg/mL, 203.02 µg/mL, 284.65 µg/mL, 1893.66 µg/mL, and 187.88 µg/mL, unlike the detection at low concentrations of 3461.19 µg/mL, 196.96 µg/mL, 664.12 µg/mL, 2835.09 µg/mL, 153.26 µg/mL, 254.43 µg/mL, 1605.00 µg/mL, 4486.02 µg/mL, and 195.60 µg/mL using UMH, for naringenin, methyl gallate, caffeic acid, rutin, ellagic acid, coumaric acid, vanillin, ferulic acid, and hesperetin, respectively. Chlorogenic acid, syringic acid, and daidzein were detected in the UMH LLE but not in the MH LLE, unlike pyrocatechol. The anti-H. pylori activity of the UMH LLE was lower (23.67 ± 0.58 mm of inhibition zone) than that of the MH LLE (26.00 ± 0.0 mm of inhibition zone). Moreover, the values of MIC and MBC associated with the MH LLE were very low compared to those of the UMH LLE. Via MBC/MIC index calculation, the UMH and MH LLEs showed cidal activity. The MH LLE exhibited higher anti-biofilm activity (93.73%) compared to the anti-biofilm activity (87.75%) of the MH LLE against H. pylori. The urease inhibition percentage was more affected in the UMH LLE compared to the MH LLE, with significant (p < 0.05) IC₅₀ values of 34.17 µg/mL and 91.11 µg/mL, respectively. Promising antioxidant activity was documented with a very low value of IC₅₀ (3.45 µg/mL) for the MH LLE compared to the IC₅₀ value of 4.69 µg/mL for the UMH LLE and the IC₅₀ value of 4.43 µg/mL for ascorbic acid. The MH LLE showed significantly higher (p < 0.05) inhibition of α-glucosidase and butyrylcholinesterase activities, with IC₅₀ values of 9.9 µg/mL and 17.3 µg/mL, respectively, compared to those of the UMH LLE at 18.36 µg/mL and 28.92 µg/mL. The molecular docking of naringenin showed good docking scores against acetylcholinesterase 1E66 and butyrylcholinesterase 6EMI, indicating that naringenin is an intriguing candidate for additional research as a possible medication for Alzheimer's disease.

Keywords: Laurus nobilis L.; anti-Alzheimer; anti-Helicobacter pylori; antidiabetic; antioxidant; naringenin.

Figure 1

Planned experiments for moist-heated (MH) and unmoist-heated laurel leaves.

Figure 2

HPLC chromatogram of identified phenolic and flavonoid constituents in unmoist-heated laurel leaf extract.

Figure 3

HPLC chromatogram of identified phenolic and flavonoid constituents in moist-heated laurel leaf extract.

Figure 4

Antimicrobial activity of UMH (A) and MH (B) laurel leaf extracts (1, negative control; 2, positive control; 3 and 4, two wells of the plant extract).

Figure 5

Anti-biofilm activity of MU LLE and UMH LLE against H. pylori: (A) microtiter plate reveals changes in stain color as a pointer of icreased anti-biofilm formation of H. Pylori (B) under different treatments of media + H. Pylori (Cont.); 25% of MBC, 50% of MBC, and 75% of MBC.

Figure 6

Urease inhibition at different concentrations of MU LLE and UMH LLE.

Figure 7

Antidiabetic activity at different concentrations of MU LLE and UMH LLE.

Figure 8

Anti-Alzheimer’s activity at different concentrations of MU LLE and UMH LLE.

Figure 9

Molecular docking process of naringenin with 1E66.

Figure 9

Molecular docking process of naringenin with 1E66.

Figure 10

Molecular docking process of naringenin with 6EMI.