The Monoterpenoid Perillyl Alcohol: Anticancer Agent and Medium to Overcome Biological Barriers

Oxidation of myrtenol to myrtenal epoxide in a porphyrin-based photocatalytic system - A novel terpene alcohol derivative with antimicrobial and anticancer properties

Biomimetic catalysis using porphyrins enables gentle oxidation of terpenes with molecular oxygen and light. This study explores the photooxidation of (-)-myrtenol under visible light to synthesize new terpenoid products with promising biological activity. Among the porphyrins tested, tetraphenylporphyrin (H2TPP) exhibited the highest catalytic efficiency and stability in chloroform, producing myrtenal epoxide (ME) as the main product (with a molar conversion of myrtenol of 66.2 %), confirmed by NMR and MS analyses. Other substrates, i.e. perillyl alcohol and trans-pinocarveol, did not yield redox products. The antimicrobial activity of ME was assessed against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans using Disk Diffusion, Minimal Inhibitory Concentration, and Minimal Biofilm Eradication Concentration assays (using liquid ME) and the Quantitative Assay for Measuring the Antibiofilm Activity of Volatile Compounds (using volatile ME). Overall, ME displayed higher antimicrobial activity than myrtenol in the majority of the tests applied. The strongest effects were observed against C. albicans, followed by S. aureus, while the weakest activity was exhibited against Gram-negative bacteria. ME also showed cytotoxic effects on human colorectal cancer cells (HT-29) with significantly higher biological activity than that of (-)-myrtenol. Notably, ME at lower concentrations (5-50 µg/ml) promoted proliferation of normal cells while inhibiting the viability and proliferation of cancer cells. Porphyrin-based photooxidation is a sustainable method for converting biorenewable terpene feedstocks into new compounds that can be used in cancer treatment and antimicrobial therapy.

Current Combinatorial Therapeutic Aspects: The Future Prospect for Glioblastoma Treatment

There are several types of brain tumors but glioblastoma (GBM) is one of the highly malignant tumors. A primary concern with GBM is that the treatment is inadequate. Even after giving many multi-stacked combinations of therapies to patients, inclusive of chemotherapy, radiation, and surgery, the median survival rate remains poor. Due to its heterogeneous nature, the use of selective therapy for specific targeting of tumor cells is of particular importance. Although many treatment alternatives which include surgery with adjuvant chemotherapy and radiotherapy are available, the prognosis of the disease is very poor. Combination therapy is becoming the foundation of modern antitumor therapy and it is continuously evolving and developing innovative drug regimens as evidenced by ongoing preclinical and clinical trials. In this review, we discuss the current treatment options and emerging therapeutic approaches for the treatment of GBM. The prospects for alternative glioblastoma therapy are also discussed.

Activation of the Nrf2/Keap1 signaling pathway mediates the neuroprotective effect of Perillyl alcohol against cerebral hypoxic-ischemic damage in neonatal rats

Neonatal hypoxic-ischemic encephalopathy (HIE) is a severe disease with a poor prognosis, whose clinical treatment is still limited to therapeutic hypothermia with limited efficacy. Perillyl alcohol (POH), a natural monoterpene found in various plant essential oils, has shown neuroprotective properties, though its effects on HIE are not well understood. This study investigates the neuroprotective effects of POH on HIE both in vitro and in vivo. We established an in vitro model using glucose deprivation and hypoxia/reperfusion (OGD/R) in PC12 cells, alongside an in vivo model via the modified Rice-Vannucci method. Results indicated that POH acted as an indirect antioxidant, reducing inducible nitric oxide synthase and malondialdehyde production, maintaining content of antioxidant molecules and enzymes in OGD/R-induced PC12 cells. In vivo, POH remarkably lessened infarct volume, reduced cerebral edema, accelerated tissue regeneration, and blocked reactive astrogliosis after hypoxic-ischemic brain injury. POH exerted antiapoptotic activities through both the intrinsic and extrinsic apoptotic pathways. Mechanistically, POH activated Nrf2 and inactivated its negative regulator Keap1. The use of ML385, a Nrf2 inhibitor, reversed these effects. Overall, POH mitigates neuronal damage in HIE by combating oxidative stress, reducing inflammation, and inhibiting apoptosis via the Nrf2/Keap1 pathway, suggesting its potential for HIE treatment.

Metabolic and Regulatory Pathways Involved in the Anticancer Activity of Perillyl Alcohol: A Scoping Review of In Vitro Studies

BACKGROUND/OBJECTIVES

Perillyl alcohol (POH), a plant-derived compound, has demonstrated anti-tumor activity across various human cancers. Understanding the regulatory pathways through which POH exerts its effects is crucial for identifying new therapeutic opportunities and exploring potential drug repositioning strategies. Therefore, this scoping review aims to provide a comprehensive overview of the metabolic and regulatory pathways involved in the anticancer effects of POH, based on in vitro evidence.

METHODS

Following the PRISMA-ScR 2018 guidelines, a systematic search was conducted in the PUBMED, Web of Science, and Scopus databases.

RESULTS

A total of 39 studies were included, revealing that POH exerts its biological effects by modulating several pathways, including the regulation of cyclins, CDKs, and p21, thereby affecting cell cycle progression. It inhibits growth and promotes cell death by attenuating AKT phosphorylation, reducing PARP-1 activity, increasing caspase activity and the FAS receptor and its ligand FASL. Additionally, POH reduces ERK phosphorylation, inhibits RAS protein isoprenylation, and decreases Na/K-ATPase activity.

CONCLUSIONS

In conclusion, this review delineates the key regulatory pathways responsible for mediating the biological effects of POH in cancer.

Epoxidation of perillyl alcohol by engineered bacterial cytochrome P450 BM3

Perillyl alcohol (POH) is a secondary metabolite of plants. POH and its derivatives are known to be effective as an anticancer treatment. In this study, oxidative derivatives of POH, which are difficult to synthesize chemically, were synthesized using the engineered bacterial cytochrome P450 BM3 (CYP102A1) as a biocatalyst. The activity of wild-type (WT) CYP102A1 and 29 engineered enzymes toward POH was screened using a high-performance liquid chromatography. They produced one major product. Among them, the engineered CYP102A1 M601 mutant with seven mutations (R47L/F81I/F87V/E143G/L150F/L188Q/E267V) showed the highest conversion, 6.4-fold higher than the WT. Structure modeling using AlphFold2 and PyMoL suggests that mutations near the water channel may be responsible for the increased catalytic activity of the M601 mutant. The major product was identified as a POH-8,9-epoxide by gas chromatography-mass spectrometry and nuclear magnetic resonance analysis. The optimal temperature and pH for the product formation were 35 °C and pH 7.4, respectively. The kcat and Km of M601 were 540 min-1 and 2.77 mM, respectively. To improve POH-8,9-epoxide production, substrate concentration and reaction time were optimized. The optimal condition for POH-8,9-epoxide production by M601 was 5.0 mM POH, pH 7.4, 35 ℃, and 6 h reaction, which produced the highest concentration of 1.72 mM. Therefore, the biosynthesis of POH-8,9-epoxide using M601 as a biocatalyst is suggested to be an efficient and sustainable synthetic process that can be applied to chemical and pharmaceutical industries.

Molecular pharmacology and therapeutic advances of monoterpene perillyl alcohol

BACKGROUND

Perillyl alcohol (POH) is a aroma monoterpene commonly obtained from various plants' essential oil. Recently, increasing researches have demonstrated that POH may be useful, not only as flavor compound, but also as bioactive molecule because of a variety of biological activities.

PURPOSE

The aim of this review is to summarize the production, pharmacological activities and molecular mechanism, active derivatives, toxicity and parmacokinetics, and industrial application of POH.

METHODS

A systematic search of published articles up to January 2024 in Web of Science, China Knowledge Network, and PubMed databases is conducted using the following keywords: POH, POH derivatives, biological or pharmacological, production or synthesis, pharmacokinetics, toxicity and application.

RESULTS

Biotechnological production is considered to be a potential alternative approach to generate POH. POH provides diverse pharmacological benefits, including anticancer, antimicrobial, insecticidal, antioxidant, anti-inflammatory, hypotensive, vasorelaxant, antinociceptive, antiasthmatic, hepatoprotective effects, etc. The underlying mechanisms of action include modulation of NF-κB, JNK/c-Jun, Notch, Akt/mTOR, PI3K/Akt/eNOS, STAT3, Nrf2 and ERS response pathways, mitigation of mitochondrial dysfunction and membrane integrity damage, and inhibition of ROS accumulation, pro-inflammatory cytokines release and NLRP3 activation. What's more, the proteins or genes influenced by POH against diseases refer to Bax, Bcl-2, cyclin D1, CDK, p21, p53, HIF-1α, AP-1, caspase-3, M6P/IGF2R, PARP, VEGF, etc. Some clinical studies report that intranasal delivery of POH is a safe and effective treatment for cancer, but further clinical investigations are needed to confirm other health benefits of POH in human healthy. Depending on these health-promoting properties together with desirable flavor and safety, POH can be employed as dietary supplement, preservative and flavor additive in food and cosmetic fields, as building block in synthesis fields, as anticancer drug in medicinal fields, and as pesticides and herbicides in agricultural fields.

CONCLUSION

This review systematically summarizes the recent advances in POH and highlights its therapeutic effects and potential mechanisms as well as the clinical settings, which is helpful to develop POH into functional food and new candidate drug for prevention and management of diseases. Future studies are needed to conduct more biological activity studies of POH and its derivatives, and check their clinical efficacy and potential side effects.

Therapeutic effect of NEO400, perillyl alcohol conjugated to linoleic acid, in a mouse model of UV-induced skin damage

Excessive exposure to ultraviolet radiation (UVR) causes harmful effects on human skin. Pre-exposure application of sunscreen can be protective, but not after damage already has occurred. There is a need for agents that can be applied post-UVR exposure to repair the damage. We investigated a novel compound, NEO400, that appears to meet this medicinal need. NEO400 was created by conjugating linoleic acid to perillyl alcohol. UVR was repeatedly administered to the skin of mice over several weeks, where it caused the typical signs of UV damage, including scaling of the skin, DNA damage, and elevated levels of inflammatory cytokines. However, when NEO400 was applied immediately post-UVR, it triggered the appearance of markers for dermal stem cell proliferation, and no signs of skin damage emerged. Furthermore, when NEO400 was applied to skin that already had incurred significant damage, it accelerated skin healing. When applied individually, linoleic acid and perillyl alcohol were ineffective, indicating that they had to be conjugated in order to exert therapeutic efficacy. None of these skin-protective effects could be achieved with Aloe vera gel, a popular and widely used post-exposure remedy. Our study suggests that NEO400 holds potential as a regenerative treatment for excessively UVR-exposed skin.

Enhancing the Antiproliferative Activity of Perillyl Alcohol against Glioblastoma Cell Lines through Synergistic Formulation with Natural Oils

BACKGROUND

Due to its volatility, photostability, and gastrointestinal toxicity, Perillyl Alcohol (POH), a monoterpenoid component of various plant species, is a chemotherapeutic drug with insufficient efficacy. Many naturally occurring bioactive compounds have well-known antiproliferative properties, including sefsol, jojoba, tea tree, and moringa oils.

OBJECTIVE

This study sought to develop an oil-based Self Nanoemulsifying Drug Delivery System (SNEDDS) using tween 80 as the surfactant and Dimethyl Sulfoxide (DMSO) or Polyethylene Glycol (PEG) 400 as the cosurfactant; the oils were used in a range of 10-20% to boost POH's anticancer efficacy.

METHODS

The formulations' size, charge, and impact on the viability of glioma cell lines, ANGM-CSS and A172, were evaluated.

RESULTS

The developed SNEDDS formulations ranged from 3 nm to 362 nm in size, with electronegative surface charges between 5.05 and 17.0 mV and polydispersity indices between 0.3 and 1.0.

CONCLUSION

The findings indicated that the antiproliferative effect of POH-loaded Nanoemulsion (NE) could be used as a possible anticancer therapy for glioblastoma in vitro, particularly when paired with the tested natural oils. Before asserting that this delivery technique is appropriate for glioblastoma therapy, additional in vitro and in vivo investigations are required.

Perillyl Alcohol Promotes Relaxation in Human Umbilical Artery

BACKGROUND

Perillyl alcohol (POH) is a monoterpenoid found in plant essential oils and has been shown to relax murine vessels, but its effect on human vessels remains poorly studied.

OBJECTIVE

The study aimed to characterize the effect of POH on human umbilical arteries (HUA).

METHODS

Rings of HUA were obtained from uncomplicated patients and suspended in an organ bath for isometric recording. The vasorelaxant effect of POH in HUA was evaluated on basal tone and electromechanical or pharmacomechanical contractions, and possible mechanisms of action were also investigated.

RESULTS

POH (1-1000 μM) altered the basal tone of HUA and completely relaxed HUA rings precontracted with KCl (60 mM) or 5-HT (10 μM), obtaining greater potency in the pharmacomechanical pathway (EC50 110.1 μM), suggesting a complex interference in the mobilization of extra- and intracellular Ca2+. POH (1000 μM) inhibited contractions induced by BaCl2 (0.1-30 mM) in a similar way to nifedipine (10 μM), indicating a possible blockade of L-type VOCC. In the presence of potassium channel blockers, tetraethylammonium (1 mM), 4-aminopyridine (1 mM), or glibenclamide (10 μM), an increase in the EC50 value of the POH was observed, suggesting a modulation of the activity of BKCa, KV, and KATP channels.

CONCLUSION

The data from this study suggest that POH modulates Ca2+ and K+ ion channels to induce a relaxant response in HUA.

Nucleophilic aromatization of monoterpenes from isoprene under nickel/iodine cascade catalysis

As a large number of organic compounds possessing two isoprene units, monoterpenes and monoterpenoids play important roles in pharmaceutical, cosmetic, agricultural, and food industries. In nature, monoterpenes are constructed from geranyl pyrophosphate (C10) via various transformations. Herein, the bulk C5 chemical-isoprene, is used for the creation of various monoterpenoids via a nucleophilic aromatization of monoterpenes under cascade catalysis of nickel and iodine. Drugs and oil mixtures from conifer and lemon can be convergently transformed to the desired monoterpenoid. Preliminary mechanistic studies are conducted to get insights about reaction pathway. Two types of cyclic monoterpenes can be respectively introduced onto two similar heterocycles via orthogonal C-H functionalization. And various hybrid terpenyl indoles are programmatically assembled from abundant C5 or C10 blocks. This work not only contributes a high chemo-, regio-, and redox-selective transformation of isoprene, but also provides a complementary approach for the creation of unnatural monoterpenoids.

Incorporation of Perillyl Alcohol into Lipid-Based Nanocarriers Enhances the Antiproliferative Activity in Malignant Glioma Cells

Perillyl alcohol (PA), a naturally existing monocyclic terpene related to limonene, is characterized by its poor aqueous solubility and very limited bioavailability. Its potential anti-cancer activity against malignant glioma has been reported. The aim was to develop PA-loaded lipid-based nanocarriers (LNCs), and to investigate their anti-cancer activity against two different brain cell lines. Non-medicated and PA-loaded LNCs were prepared and characterized. The mechanism of cytotoxic activity of PA was conducted using a molecular docking technique. The cell viabilities against A172 and ANGM-CSS cells were evaluated. The results revealed that the average particle size of the prepared LNCs ranged from 248.67 ± 12.42 to 1124.21 ± 12.77 nm, the polydispersity index was 0.418 ± 0.043-0.509 ± 0.064, while the zeta potential ranged from -36.91 ± 1.31 to -15.20 ± 0.96 mV. The molecular docking studies demonstrated that the drug had binding activity to human farnesyltransferase. Following exposure of the two glioblastoma cell lines to the PA-loaded nanoformulations, MTS assays were carried out, and the data showed a far lower half-maximal inhibitory concentration in both cell lines when compared to pure drug and non-medicated nanocarriers. These results indicate the potential in vitro antiproliferative activity of PA-loaded LNCs. Therefore, the prepared PA-loaded nanocarriers could be used to enhance drug delivery across the blood-brain barrier (BBB) in order to treat brain cancer, especially when formulated in a suitable dosage form. The size, surface charge, and lipid composition of the LNCs make them promising for drug delivery across the BBB. Detailed pharmacokinetic and pharmacodynamic assessments, including the evaluation of BBB penetration, are necessary to better understand the compound's distribution and effects within the brain.

Phytochemicals for the prevention and treatment of pancreatic cancer: Current progress and future prospects

Pancreatic cancer is the third leading cause of cancer-related deaths in the United States, owing to its aggressive nature and suboptimal treatment options, emphasizing the need for novel therapeutic approaches. Emerging studies have exhibited promising results regarding the therapeutic utility of plant-derived compounds (phytochemicals) in pancreatic cancer. The purpose of this review is to evaluate the potential of phytochemicals in the treatment and prevention of pancreatic cancer. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was applied to collect articles for this review. Scholarly databases, including PubMed, Scopus and ScienceDirect, were queried for relevant studies using the following keywords: phytochemicals, phenolics, terpenoids, alkaloids, sulfur-containing compounds, in vitro, in vivo, clinical studies, pancreatic cancer, tumour, treatment and prevention. Aggregate results pooled from qualified studies indicate phytochemicals can inhibit pancreatic cancer cell growth or decrease tumour size and volume in animal models. These effects have been attributed to various mechanisms, such as increasing proapoptotic factors, decreasing antiapoptotic factors, or inducing cell death and cell cycle arrest. Notable signalling pathways modulated by phytochemicals include the rat sarcoma/mitogen activated protein kinase, wingless-related integration site/β-catenin and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signal transduction pathways. Clinically, phytochemicals have been found to increase survival while being well-tolerated and safe, though research is scarce. While these promising results have produced great interest in this field, further in-depth studies are required to characterize the anticancer activities of phytochemicals before they can be utilized to prevent or treat pancreatic cancer in clinical practice.

Enhancing Oral Bioavailability and Brain Biodistribution of Perillyl Alcohol Using Nanostructured Lipid Carriers

Perillyl alcohol (POH), a bioactive monoterpenoid derived from limonene, shows promise as an antitumor agent for brain tumor treatment. However, its limited oral bioavailability and inadequate brain distribution hinder its efficacy. To address these challenges, this study developed nanostructured lipid carriers (NLCs) loaded with POH to improve its brain biodistribution. The NLCs prepared using hot homogenization exhibited an average diameter of 287 nm and a spherical morphology with a polydispersity index of 0.143. High encapsulation efficiency of 99.68% was achieved. X-ray diffraction analyses confirmed the semicrystalline state of POH-loaded NLCs. In vitro release studies demonstrated a biphasic release profile. Stability studies in simulated gastric and intestinal fluids confirmed their ability to withstand pH variations and digestive enzymes. In vivo pharmacokinetic studies in rats revealed significantly enhanced oral bioavailability of POH when encapsulated in the NLCs. Biodistribution studies showed increased POH concentration in brain tissue with NLCs compared with free POH, which was distributed more in non-target tissues such as the liver, lungs, kidneys, and spleen. These findings underscore the potential of NLCs as effective delivery systems for enhancing oral bioavailability and brain biodistribution of POH, providing a potential therapeutic strategy for brain tumor treatment.

Intranasal Delivery of miR133b in a NEO100-Based Formulation Induces a Healing Response in Spinal Cord-Injured Mice

Despite important advances in the pre-clinical animal studies investigating the neuroinhibitory microenvironment at the injury site, traumatic injury to the spinal cord remains a major problem with no concrete response. Here, we examined whether (1) intranasal (IN) administration of miR133b/Ago2 can reach the injury site and achieve a therapeutic effect and (2) NEO100-based formulation of miR133b/Ago2 can improve effectiveness. 24 h after a cervical contusion, C57BL6 female mice received IN delivery of miR133b/Ago2 or miR133b/Ago2/NEO100 for 3 days, one dose per day. The pharmacokinetics of miR133b in the spinal cord lesion was determined by RT-qPCR. The role of IN delivery of miR133b on motor function was assessed by the grip strength meter (GSM) and hanging tasks. The activity of miR133b at the lesion site was established by immunostaining of fibronectin 1 (FN1), a miR133b target. We found that IN delivery of miR133b/Ago2 (1) reaches the lesion scar and co-administration of miR133b with NEO100 facilitated the cellular uptake; (2) enhanced the motor function and addition of NEO100 potentiated this effect and (3) targeted FN1 expression at the lesion scar. Our results suggest a high efficacy of IN delivery of miR133b/Ago2 to the injured spinal cord that translates to improved healing with NEO100 further potentiating this effect.

The Fractal Viewpoint of Tumors and Nanoparticles

Even though the promising therapies against cancer are rapidly improved, the oncology patients population has seen exponential growth, placing cancer in 5th place among the ten deadliest diseases. Efficient drug delivery systems must overcome multiple barriers and maximize drug delivery to the target tumors, simultaneously limiting side effects. Since the first observation of the quantum tunneling phenomenon, many multidisciplinary studies have offered quantum-inspired solutions to optimized tumor mapping and efficient nanodrug design. The property of a wave function to propagate through a potential barrier offer the capability of obtaining 3D surface profiles using imaging of individual atoms on the surface of a material. The application of quantum tunneling on a scanning tunneling microscope offers an exact surface roughness mapping of tumors and pharmaceutical particles. Critical elements to cancer nanotherapeutics apply the fractal theory and calculate the fractal dimension for efficient tumor surface imaging at the atomic level. This review study presents the latest biological approaches to cancer management based on fractal geometry.

NEO212, a Perillyl Alcohol-Temozolomide Conjugate, Triggers Macrophage Differentiation of Acute Myeloid Leukemia Cells and Blocks Their Tumorigenicity

Many patients with acute myeloid leukemia (AML) are still dying from this disease. In the past, the alkylating agent temozolomide (TMZ) has been investigated for AML and found to be partially effective; however, the presence of O6-methylguanine DNA methyltransferase (MGMT; a DNA repair enzyme) in tumor cells confers profound treatment resistance against TMZ. We are developing a novel anticancer compound, called NEO212, where TMZ was covalently conjugated to perillyl alcohol (a naturally occurring monoterpene). NEO212 has revealed robust therapeutic activity in a variety of preclinical cancer models, including AML. In the current study, we investigated its impact on a panel of human AML cell lines and found that it exerted cytotoxic potency even against MGMT-positive cells that were highly resistant to TMZ. Furthermore, NEO212 strongly stimulated the expression of a large number of macrophage-associated marker genes, including CD11b/ITGAM. This latter effect could not be mimicked when cells were treated with TMZ or an equimolar mix of individual agents, TMZ plus perillyl alcohol. The superior cytotoxic impact of NEO212 appeared to involve down-regulation of MGMT protein levels. In a mouse model implanted with TMZ-resistant, MGMT-positive AML cells, two 5-day cycles of 25 mg/kg NEO212 achieved an apparent cure, as mice survived >300 days without any signs of disease. In parallel toxicity studies with rats, a 5-day cycle of 200 mg/kg NEO212 was well tolerated by these animals, whereas animals that were given 200 mg/kg TMZ all died due to severe leukopenia. Together, our results show that NEO212 exerts pleiotropic effects on AML cells that include differentiation, proliferation arrest, and eventual cell death. In vivo, NEO212 was well tolerated even at dosages that far exceed the therapeutic need, indicating a large therapeutic window. These results present NEO212 as an agent that should be considered for development as a therapeutic agent for AML.