Gas Chromatography-Mass Spectrometry Method for Simultaneous Detection of Nine Alkaloids in Tobacco and Tobacco Products by QuEChERS Sample Preparation

An insight into recent updates on analytical techniques for bioactive alkaloids

INTRODUCTION

Alkaloids represent a wide class of naturally existing nitrogen-containing organic compounds having diverse biological activities. They are primary bioactive substances extracted from diverse plant parts. Due to their diverse biological activities, they are frequently used as medicines. The alkaloids have diverse pharmacological impacts on the human body; alkaloids are used for prevention, treatment, and reduction of discomfort associated with chronic illnesses. As most alkaloids exist in plants in complex form, combined with numerous other natural plant components, it is essential to recognize and characterize these molecules using different analytical techniques.

OBJECTIVES

We aimed to review the literature on the methods and protocols for the analysis of naturally occurring alkaloids.

METHODS

We carried out a literature survey using the PubMed, Scopus, and Google Scholar databases and other relevant published materials. The keywords used in the searches were "alkaloids," "analytical methods," "HPLC method," "GC method," "electrochemical methods," and "bioanalytical methods," in various combinations.

RESULTS

In this article, several classes of alkaloids are presented, along with their biological activities. Moreover, it includes a thorough explanation of chromatographic techniques, hyphenated techniques, electrochemical techniques, and current trending analytical methods utilized for the isolation, identification, and comprehensive characterization of alkaloids.

CONCLUSIONS

The various analytical techniques play an important role in the identification as well as the characterization of various alkaloids from plants, plasma samples, and urine samples. The hyphenation of various chromatographic techniques with mass spectrometry and NMR spectroscopy plays a crucial role in the characterization of unknown compounds.

LC-MS/MS analysis of carcinogenic tobacco-specific nitrosamines in Spodoptera litura using the QuEChERS method

Nicotine is a highly addictive alkaloid and a neurostimulator found in tobacco that causes addiction in humans and makes tobacco a high-demand commercial product. It is popularly used for recreational purposes and is a harmful substance (Oral LD₅₀ value for rat is 50 mg/kg) and causes addiction. The metabolites of nicotine such as the Tobacco-specific Nitrosamines (TSNAs) are hazardous substances whose metabolites are highly electrophilic and form DNA adducts, which will initiate the process of carcinogenesis. TSNAs are formed during curing, storage and fermentation due to the nitrosation of nicotine and other tobacco alkaloids. TSNAs are used as biomarkers for cancer risk assessment in humans exposed to tobacco and its products. To determine the occasional formation of TSNAs in tobacco-feeding insects, 5th instar larvae of Spodoptera litura and their faeces were analyzed for the presence of N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) along with the stored tobacco leaves (PT-76) using an Agilent 6470B LC-MS/MS system following ISO/DIS 19290:2015 protocol. The larvae are extracted in a buffered acetonitrile-water extraction and the amount of TSNAs are quantified in multiple reaction monitoring (MRM) mode. 20 [Formula: see text]l of each extracted and cleaned up sample was injected into the LC-MS/MS system for quantification. The Limit of Detection (LOD) and Limit of Quantification (LOQ) were 0.001 mg/kg and 0.005 mg/kg for all the tested nitrosamines. NNN was found to be 0.361 mg/kg, 0.340 mg/kg, and 5.66 mg/kg in insect whole-body samples, faeces, and tobacco leaves, respectively. NNK was found to be 0.060 mg/kg, 0.035 mg/kg and 0.93 mg/kg in insect whole body samples, faeces and tobacco leaves, respectively. However, NNAL was not detected in both the insect's whole body and faeces. Recoveries ranged between 95 and 98% for all compounds when spiked at LOD and LOQ. The presence of TSNAs is a biomarker for cancer risk and their presence in insects would point to cancer risk assessment in tobacco feeding insects and any possible TSNA-detoxifying pathways in insects that might prevent mutagenesis caused these compounds.

Long-term organic fertilizer additions elevate soil extracellular enzyme activities and tobacco quality in a tobacco-maize rotation

Organic fertilizer is effective in improving soil quality, and promoting crop growth. Combined organic and inorganic fertilization has been proved as a more favorable way to tobacco yield and quality. However, the mechanisms underlying tobacco yield and quality under combinations of different organic and inorganic fertilizer remain unclear. We conducted a 12-year tobacco (Nicotiana tabacum L.)-maize crop rotation field experiment in Yanhe experimental station, China to examine the yields and qualities of tobacco, soil nutrients, and extracellular enzyme activities associated with carbon, nitrogen, and phosphorus cycles in response to different fertilization treatments. Five fertilization treatments (no fertilization; 75 kg N fertilizer ha^-1; 450 kg oil cake ha^-1 + 75 kg N fertilizer ha^-1; 15,000 kg pig dung ha^-1 + 60 kg N fertilizer ha^-1; 3,000 kg straw ha^-1 + 75 kg N fertilizer ha^-1) were applied to tobacco while maize was fertilized with inorganic compound fertilizers. After 12 years of tobacco-maize rotation, the results showed that organic fertilizer additions elevate tobacco yield and quality, and the soil extracellular enzymes activities. Gram-negative bacteria, actinomycetes, and total soil microbial biomass were increased by organic fertilizer additions, both plant-based (oil cake and straw) and animal-based (pig dung) organics. The levels of soil organic matter, total organic carbon, total phosphorus and available phosphorus are higher in pig dung addition treatment than oil cake and straw additions. By variance analysis with respect to fertilization treatments, organic sources differentially affected the activities of diverse soil enzymes. The redundancy analysis gave that yield and quality of tobacco leaves (upper, middle, and lower leaves) positively related to soil extracellular enzyme activities. Based on analysis of yield and quality of tobacco leaves with extracellular enzyme activities and soil nutrients, it is suggested animal-based organic fertilizer, thus pig dung, should be used in combining with chemical fertilizers to improve the quality of tobacco and soil nutrients.

Optimization of Ultrasonic-Assisted Extraction of Chlorogenic Acid from Tobacco Waste

Using tobacco waste as raw material, the ultrasonic-assisted extraction of chlorogenic acid was optimized by response surface methodology (RSM). After repeated freezing and thawing of tobacco waste twice, the effect of pH value, ethanol volume fraction, temperature and extraction time on the extraction rate of chlorogenic acid was investigated by a single factor experiment. On the basis of this, the factors affecting the yield of chlorogenic acid were further optimized by using RSM. The optimum extraction conditions for chlorogenic acid were set at pH = 4.1, ethanol volume fraction was 49.57% and extraction time was 2.06 h. Under the above conditions, the extraction rate of chlorogenic acid could reach 0.502%, which was higher than traditional extraction and unpretreated ultrasonic extraction. All these results can be used as a reference for the extraction of effective ingredients in tobacco waste.

Stable Isotope Labeling by Carbon-13 in Bacteria Culture for the Analysis of Residual Avermectin Using Stable Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry

This study describes the development of a new stable isotope labeling method by carbon-13 in bacteria culture (SILCB) for the analysis of residual antibiotics via liquid chromatography with tandem mass spectrometry (LC-MS/MS). Stable isotope dilution (SID) LC-MS/MS with QuEChERS was employed to determine avermectin, particularly avermectin B1a (AV-a) and B1b (AV-b), based on completely ¹³C-labeled internal standards (¹³C-ISs) obtained from the SILCB. Our SILCB was developed from an optimal inorganic medium using ¹³C₆-glucose for Streptomyces avermitilis (14893 strain). A rough extract containing ¹³C-ISs was purified via high-speed countercurrent chromatography with a volatile two-phase solvent system composed of n-hexane/ethyl acetate/methanol/0.5% formic acid in water (7/3/5/5/, V/V). The purified ¹³C-ISs were evaluated to confirm the presence of completely ¹³C-labeled ions with m/z 938 > 326 and m/z 923 > 309 for AV-a and AV-b, respectively. The QuEChERS approach with the ¹³C-ISs procedure achieved acceptable recovery rates in beef meat samples of 99.5 - 100.0% (RSD < 2.0%, n = 6). For the analysis of residual antibiotics in foodstuffs by SID-LC-MS/MS and QuEChERS, the SILCB represents a significant improvement over previous methods suffering from cumbersome sample preparation and matrix effects.

Comprehensive Analysis of Volatile Compounds in Mouthpiece Cigarette Adhesive by Coupling Headspace with Gas Chromatography-Mass Spectrometry

BACKGROUND

Some volatile compounds in mouthpiece cigarette adhesive emit irritating odors and affect the taste of smoking cigarettes. Therefore, it is necessary to monitor the volatile compounds in mouthpiece cigarette adhesive.

OBJECTIVES

A rapid and simple analytical method of volatile compounds in mouthpiece cigarette adhesive was established.

METHODS

In this study, headspace (HS) injection coupled with GC-MS was utilized for qualitative and quantitative analysis. Initially, the volatile compounds in mouthpiece cigarette adhesives were detected by HS-GC-MS, followed by spectrum library retrieval. The detected compounds with the similarity to a spectrum library of more than 85% were further identified by comparing the retention time and mass spectra of the detected volatile compounds and those of the corresponding standard samples. The quantitative analysis of nine identified volatile compounds was performed.

RESULTS

Eleven volatile compounds in the mouthpiece cigarette adhesive were accurately identified. The quantitative analytical method of nine volatile compounds in mouthpiece cigarette adhesive was validated to have good linearities (R2 > 0.9932) within the range of 20-5000 ng/g. The detection limits of 9 compounds were within the range of 3.1-147.7 ng/g. The intra- and inter-day relative standard deviations were less than 19.8%. The recoveries of these 9 compounds spiked into mouthpiece cigarette adhesive were 68.1-108.3%.

CONCLUSIONS

The proposed method is rapid, simple, and accurate for qualitative and quantitative analysis of volatile compounds in the mouthpiece cigarette adhesive.

HIGHLIGHTS

The developed analytical method is expected to be used to monitor volatile compounds in various adhesives.

An essay on ecosystem availability of Nicotiana glauca graham alkaloids: the honeybees case study

BACKGROUND

Invasive plant species pose a significant threat for fragile isolated ecosystems, occupying space, and consuming scarce local resources. Recently though, an additional adverse effect was recognized in the form of its secondary metabolites entering the food chain. The present study is elaborating on this subject with a specific focus on the Nicotiana glauca Graham (Solanaceae) alkaloids and their occurrence and food chain penetrability in Mediterranean ecosystems. For this purpose, a targeted liquid chromatography electrospray tandem mass spectrometric (LC-ESI-MS/MS) analytical method, encompassing six alkaloids and one coumarin derivative, utilizing hydrophilic interaction chromatography (HILIC) was developed and validated.

RESULTS

The method exhibited satisfactory recoveries, for all analytes, ranging from 75 to 93%, and acceptable repeatability and reproducibility. Four compounds (anabasine, anatabine, nornicotine, and scopoletin) were identified and quantified in 3 N. glauca flowers extracts, establishing them as potential sources of alien bio-molecules. The most abundant constituent was anabasine, determined at 3900 μg/g in the methanolic extract. These extracts were utilized as feeding treatments on Apis mellifera honeybees, resulting in mild toxicity documented by 16-18% mortality. A slightly increased effect was elicited by the methanolic extract containing anabasine at 20 μg/mL, where mortality approached 25%. Dead bees were screened for residues of the N. glauca flower extracts compounds and a significant mean concentration of anabasine was evidenced in both 10 and 20 μg/mL treatments, ranging from 51 to 92 ng/g per bee body weight. Scopoletin was also detected in trace amounts.

CONCLUSIONS

The mild toxicity of the extracts in conjunction with the alkaloid and coumarin residual detection in bees, suggest that these alien bio-molecules are transferred within the food chain, suggesting a chemical invasion phenomenon, never reported before.