In vitro antibacterial activity of nimbolide against Helicobacter pylori

ETHNOPHARMACOLOGICAL RELEVANCE

Nimbolide is one of hundreds of phytochemicals that have been identified within the neem tree (Azadirachta indica A. Juss). As an evergreen tree native to the Indian subcontinent, components of the neem tree have been used for millennia in traditional medicine to treat dental, gastrointestinal, urinary tract, and blood-related ailments, ulcers, headaches, heartburn, and diabetes. In modern times, natural oils and extracts from the neem tree have been found to have activities against a variety of microorganisms, including human pathogens.

AIM OF THE STUDY

Helicobacter pylori, a prevalent gastric pathogen, shows increasing levels of antibiotic resistance. Thus, there is an increasing demand for novel therapeutics to treat chronic infections. The in vitro activity of neem oil extract against H. pylori was previously characterized and found to be bactericidal. Given the numerous phytochemicals found in neem oil extract, the present study was designed to define and characterize specific compounds showing bactericidal activity against H. pylori.

MATERIALS AND METHODS

Azadirachtin, gedunin, and nimbolide, which are all common in neem extracts, were tested for antimicrobial activity; the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for nine strains of H. pylori. The specific properties of nimbolide were further characterized against H. pylori strain G27. Bactericidal kinetics, reversibility, effectiveness at low pH, and activity under bacteriostatic conditions were examined. The hemolytic activity of nimbolide was also measured. Finally, neem oil extract and nimbolide effectiveness against H. pylori biofilms were examined in comparison to common antibiotics used to treat H. pylori infection.

RESULTS

Nimbolide, but not azadirachtin or gedunin, was effective against H. pylori; MICs and MBCs against the nine tested strains ranged between 1.25-5 μg/mL and 2.5-10 μg/mL, respectively. Additionally, neem oil extract and nimbolide were both effective against H. pylori biofilms. Nimbolide exhibited no significant hemolytic activity at biologically relevant concentrations. The bactericidal activity of nimbolide was time- and dose-dependent, independent of active H. pylori growth, and synergistic with low pH. Furthermore, nimbolide-mediated H. pylori cell death was irreversible after exposure to high nimbolide concentrations (80 μg/mL, after 2 h of exposure time and 40 μg/mL after 8 h of exposure).

CONCLUSIONS

Nimbolide has significant bactericidal activity against H. pylori, killing both free living bacterial cells as well as cells within a biofilm. Furthermore, the lack of hemolytic activity, synergistic activity at low pH and bactericidal properties even against bacteria in a state of growth arrest are all ideal pharmacological and biologically relevant properties for a potential new agent. This study underscores the potential of neem oil extract or nimbolide to be used as a future treatment for H. pylori infection.

Emerging approaches to determine maturity of citrus fruit

Owing to their health-boosting properties and other appreciable properties, citrus fruit is widely consumed and commercialized worldwide. Destination markets around the world vary in their fruit quality requirements and are also highly influenced by climatic conditions, agronomical and postharvest practices. Hence, harvesting decisions are arduous. Maturity indices in citrus fruit are highly variable and dependent on the species and varieties, growing regions, and destination markets. For decades, determination of the maturity of citrus fruit and predicting the near time of harvesting was a challenge for producers, researchers, and food safety agencies. Thus, the current review provides a correlation between maturity and internal components and an overview of techniques of maturity determination for citrus fruits. Also, stress has been given to the destructive and nondestructive methods to determine the maturity level of different citrus species. The techniques presented in this review portray continuous productiveness as an excellent quality assessment, particularly as ripening and maturity analysis tools for citrus fruits. Traditional techniques are time-consuming, laborious, costly, destructive, and tedious. Thus, these nondestructive techniques hold great potential to replace conventional procedures.

Variation in limonin and nomilin content in citrus fruits of eight varieties determined by modified HPLC

The nomilin and limonin content in citrus fruits of different varieties was determined at fruit growth and maturation stages by HPLC. The results showed that the two limonoids can be separated, identified, and quantified in citrus fruits within 10 min by the developed method. The method exhibited good precision, repeatability, stability, and recovery rate. The content of limonin and nomilin in most citrus fruits presented an increasing trend initially, and then decreased during fruit growth and maturation; a peak was observed at the young fruit or fruit expansion stage. The dropped fruits also contained some amount of limonoids, suggesting their industrial application. The variation and cluster analyses results revealed that the orange varieties contained the highest amount of limonoids at the mature stage. The results of this study will enable better use of citrus limonoids.

A Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Nimbolide in Mouse Serum: Application to a Preclinical Pharmacokinetics Study

A sensitive and robust liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of nimbolide in mouse serum. Exemestane was used as the internal standard (IS). Here, we employed acetonitrile-based protein precipitation (PPT) for serum sample preparation, and performed chromatographic separation using an ODS Hypersil C18 column (100 mm × 2.1 mm, 5 µm) with gradient elution (0.1% formic acid in water vs 100% acetonitrile). The run time was 6 min. Instrumental analysis was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the multiple-reaction monitoring (MRM) under positive mode. A good linear calibration was achieved in the 5–1000 ng/mL range. The intra- and inter-day precisions for nimbolide were ≤12.6% and ≤13.9% respectively. Intra-day accuracy ranged from 96.9–109.3%, while inter-day accuracy ranged from 94.3–110.2%. The matrix effect of nimbolide, detected but consistent at low and high concentrations, do not affect linearity of standard curve. In conclusion, we have developed and validated a sensitive analytical method for determination of a novel natural compound nimbolide in mouse serum, and it has been successfully applied to our preclinical study in investigating the pharmacokinetic properties of nimbolide, which could greatly facilitate the preclinical development of the promising lead compound for anticancer therapy.

Evaluation of Apoptosis and Autophagy Inducing Potential of Berberis aristata, Azadirachta indica, and Their Synergistic Combinations in Parental and Resistant Human Osteosarcoma Cells

Cancer is a multifactorial disease and hence can be effectively overcome by a multi-constituently therapeutic strategy. Medicinal plant extracts represent a perfect example of such stratagem. However, minimal studies have been done till date that portray the effect of extraction techniques on the phyto-constituent profile of plant extracts and its impact on anticancer activity. In the present study, we have evaluated the anticancer potential of methanolic extracts of Berberis aristata root and Azadirachta indica seeds prepared by various extraction techniques in human osteosarcoma (HOS) cells. Soxhlation extract of B. aristata (BAM-SX) and sonication extract of A. indica (AIM-SO) were most effective in inducing apoptosis in parental drug sensitive, as well as resistant cell type developed by repeated drug exposure. Generation of reactive oxygen species and cell cycle arrest preceded caspase-mediated apoptosis in HOS cells. Interestingly, inhibition of autophagy enhanced cell death suggesting the cytoprotective role of autophagy. Combination studies of different methanolic extracts of BAM and AIM were performed, among which, the combination of BAM-SO and AIM-SO (BAAISO) was found to show synergism (IC₅₀ 10.27 µg/ml) followed by combination of BAM-MC and AIM-MC (BAAIMC) with respect to other combinations in the ratio of 1:1. BAAISO also showed synergism when it was added to cisplatin-resistant HOS cells (HCR). Chromatographic profiling of BAM-SX and AIM-SO by high performance thin layer chromatography resulted in identification of berberine (R_f 0.55), palmitine (R_f 0.50) in BAM-SX and azadirachtin A (R_f 0.36), azadirachtin B (R_f 0.56), nimbin (R_f 0.80), and nimbolide (R_f 0.43) in AIM-SO. The cytotoxic sensitivity obtained can be attributed to the above compounds. Our results highlight the importance of extraction technique and subsequent mechanism of action of multi-constituential B. aristata and A. indica against both sensitive and drug refractory HOS cells.