Comparative Study of Chemical Composition, Cholinesterase Inhibition and Antioxidant Potential of Mentha pulegium L. Essential Oil

Chemical composition and anticholinesterase activity of Lepisanthes rubiginosa (Roxb.) Leenh. essential oil

Essential oils obtained from medicinal plants show high therapeutic potential against several types of pathologies, including Alzheimer’s disease. The purpose of this work was to study the chemical composition and anticholinesterase inhibitory activity of the essential oil obtained from Lepisanthes rubiginosa leaves collected from Malaysia. Twenty-four components were identified using gas chromatography-flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC-MS), which represent 99.5% of the essential oil. The identified major components include α-cadinol (40.0%), safrole (12.6%), α-amorphene (9.5%), (E)-isosafrole (5.0%), δ-cadinene (4.2%), and t-muurolol (4.1%). Anticholinesterase activity was assessed using Ellman method, and the essential oil demonstrated a moderate inhibitory activity against acetylcholinesterase (I%: 75.2%) and butyrylcholinesterase (I%: 70.2%) at conconcetration of 1000 μg/mL. The current study is the first to report chemical composition and anticholinesterase activity of the essential oil obtained from L. rubiginosa, which may have implications on the characterization, pharmaceutical, and therapeutic applications of Lepisanthes genus essential oils.

Molecular Interaction Studies and Phytochemical Characterization of Mentha pulegium L. Constituents with Multiple Biological Utilities as Antioxidant, Antimicrobial, Anticancer and Anti-Hemolytic Agents

Multiple biological functions of Mentha pulegium extract were evaluated in the current work. Phytochemical components of the M. pulegium extract were detected by Gas Chromatography-Mass Spectrometry (GC-MS) and High-performance liquid chromatography (HPLC). Moreover, M. pulegium extract was estimated for antioxidant potential by 2,2-Diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical scavenging, antimicrobial activity by well diffusion, and anticoagulant activity via prothrombin time (PT) and activated partial thromboplastin time (APTT). GC-MS analysis detected compounds including cholesterol margarate, stigmast-5-en-3-ol, 19-nor-4-androstenediol, androstan-17-one, pulegone-1,2-epoxide, isochiapin B, dotriacontane, hexadecanoic acid and neophytadiene. Chrysoeriol (15.36 µg/mL) was followed by kaempferol (11.14 µg/mL) and 7-OH flavone (10.14 µg/mL), catechin (4.11 µg/mL), hisperdin (3.05 µg/mL), and luteolin (2.36 µg/mL) were detected by HPLC as flavonoids, in addition to ferulic (13.19 µg/mL), cinnamic (12.69 µg/mL), caffeic (11.45 µg/mL), pyrogallol (9.36 µg/mL), p-coumaric (5.06 µg/mL) and salicylic (4.17 µg/mL) as phenolics. Antioxidant activity was detected with IC50 18 µg/mL, hemolysis inhibition was recorded as 79.8% at 1000 μg/mL, and PT and APTT were at 21.5 s and 49.5 s, respectively, at 50 μg/mL of M. pulegium extract. The acute toxicity of M. pulegium extract was recorded against PC3 (IC50 97.99 µg/mL) and MCF7 (IC50 80.21 µg/mL). Antimicrobial activity of M. pulegium extract was documented against Bacillus subtilis, Escherichia coli, Pseudomonasaureus, Candida albicans, Pseudomonas aeruginosa, but not against black fungus Mucor circinelloides. Molecular docking was applied using MOE (Molecular Operating Environment) to explain the biological activity of neophytadiene, luteolin, chrysoeriol and kaempferol. These compounds could be suitable for the development of novel pharmacological agents for treatment of cancer and bacterial infections.

Effect of Extraction Methods on Polyphenols, Flavonoids, Mineral Elements, and Biological Activities of Essential Oil and Extracts of Mentha pulegium L

Our study evaluated the in vitro antioxidant properties, antibacterial and antifungal activities, anti-inflammatory properties, and chemical composition of the essential oils (EOs), total phenol, and total flavonoid of wild Mentha pulegium L. This study also determined the mineral (nutritional and toxic) elements in the plant. The EOs were extracted using three techniques-hydro distillation (HD), steam distillation (SD), and microwave-assisted distillation (MAD)-and were analyzed using chromatography coupled with flame ionization (GC-FID) and gas chromatography attached with mass spectrometry detector (GC-MS). The antioxidant effects of the EOs were tested with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), while the antibacterial and antifungal activities of the EO and methanolic extract were tested using Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. Twenty-six compounds were identified in the essential oil, representing 97.73% of the total oil, with 0.202% yield. The major components were pulegone (74.81%), menthone (13.01%) and piperitone (3.82%). Twenty-one elements, including macro- and micro-elements (Ba, Br, Ca, Cl, Co, Cr, Cs, Eu, Fe, K, Mg, Mn, Mo, Na, Rb, Sb, Sc, Sr, Th, U and Zn), were detected using neutron activation analysis (INAA) and inductively coupled plasma optical emission spectrometry (ICP-OES), with the concentration of mineral element close to the FAO recommendation. The results show that the EOs and extracts from Mentha pulegium L. had significant antimicrobial activities against the microorganisms, including five human pathogenic bacteria, one yeast (Candida albicans), and one phytopathogenic fungi. The in vivo anti-inflammatory activities of the leaf extracts were confirmed. The results indicate that the EOs and extracts from Mentha pulegium L. have promising applications in the pharmaceutical industries, clinical applications, and in medical research.

Evaluation of Enzyme Inhibition and Anti-Quorum Sensing Potentials of Melaleuca alternifolia and Citrus sinensis Essential Oils

In this study, Melaleuca alternifolia (Maiden and Betche) Cheel (tea tree) oil and C. sinensis (L.) Osbeck (orange) oil was procured, and their chemical compositions were characterized by gas chromatography coupled with mass spectrometry, with co-injection using authentic samples. The oils were rich in monoterpene hydrocarbons making up 84.5% of C. sinensis and 48.9% of M. alternifolia oils. High amounts of oxygenated monoterpenoids were also identified in C. sinensis (9.6%) and M. alternifolia (49.3%) oils. The three most abundant compounds were limonene (71.2%), linalool (5.5%), and β-myrcene (5.1%) in C. sinensis, and terpinen-4-ol (45.6%), γ-terpinene (19.4%) and α-terpinene (9.3%) in M. alternifolia. Enzyme inhibitions (anticholinesterase, antiurease, antityrosinase) of both essential oils were evaluated. In acetylcholinesterase assay, M. alternifolia and C. sinensis had inhibition concentration (IC50) values of 153.7 ± 1.25 and 96.4 ± 1.0 µg/mL, respectively as compared to 5.42 ± 0.11 µg/mL for galantamine, while in butyrylcholinesterase assay, M. alternifolia (IC50 = 85.6 ± 0.7 µg/mL) and C. sinensis (IC50 = 127.8 ± 0.6 µg/mL) exhibited moderate activities compared to galantamine (IC50 = 45.8 ± 0.8 µg/mL). In the urease inhibitory activity, essential oils of C. sinensis and M. alternifolia showed 48.4% ± 0.9% and 30.6% ± 0.7% inhibitions at 200 µg/mL concentration, respectively. Quorum sensing (QS) mediated violacein production in Chromobacterium violaceum CV12472 was inhibited by 100% at minimum inhibitory concentration (MIC) values for both oils while showing QS inhibition diameter zones in C. violaceum of 22.5 ± 0.4 mm and 14.3 ± 0.5 mm for C. sinensis and M. alternifolia oils, respectively at MIC concentration. The good quorum-sensing potential indicates that these oils can suppress microbial resistance and severity of infections.

Flavour chemicals, synthetic coolants and pulegone in popular mint-flavoured and menthol-flavoured e-cigarettes

Background

The Food and Drug Administration (FDA) has recently banned flavours from pod-style electronic cigarettes (e-cigarettes), except for menthol and tobacco. JUUL customers have quickly discovered that flavoured disposable e-cigarettes from other manufacturers, such as Puff, are readily available. Our goal was to compare flavour chemicals, synthetic coolants and pulegone in mint-flavoured/menthol-flavoured e-cigarettes from JUUL and Puff, evaluate the cytotoxicity of the coolants and perform a cancer risk assessment for pulegone, which is present in both JUUL pods and disposable Puff products.

Methods

Identification and quantification of chemicals were performed using gas chromatography/mass spectrometry. Cytotoxicity of the coolants was evaluated with BEAS-2B cells using the MTT 3-(4,5-dimethylthiazol-2-yl)−2,5-diphenyltetrazolium bromide assay. The cancer risk of pulegone was calculated using the margin of exposure (MOE).

Results

Menthol was the dominant flavour chemical (>1 mg/mL) in all products from both manufacturers. Minor flavour chemicals (<1 mg/mL) differed in the JUUL and Puff fluids and may produce flavour accents. The concentrations of WS-3 and WS-23 were higher in Puff than in JUUL. WS-23 was cytotoxic in the MTT assay at concentrations 90 times lower than concentrations in Puff fluids. The risk of cancer (MOE<10 000) was greater for mint than for menthol products and greater for Puff than for JUUL.

Conclusions

Switching from flavoured JUUL to Puff e-cigarettes may expose users to increased harm due to the higher levels of WS-23 and pulegone in Puff products. Cancer risk may be reduced in e-cigarettes by using pure menthol rather than mint oils to produce minty-flavoured e-cigarette products.