Understanding the postmortem changes in concentrations of methanol in ocular matrices in rabbits.

Death due to abuse and accidental ingestion of methanol is widely known around the globe. The paper presents the postmortem changes in concentrations of methanol in the vitreous humor, aqueous humor, and ocular tissues in a rabbit model in methanol intoxication. Rabbits were intoxicated with methanol at a dose of 6.3 ml/kg through oral gavage. After 3.5 h of methanol administration, the rabbits were sacrificed. Vitreous humor, aqueous humor, and ocular tissues were collected both, perimortem (immediately) and postmortem (17 h post-death). Whole blood and plasma samples were also collected to explore the correlation between levels of methanol in whole blood/plasma and ocular fluids/ocular tissues if any. All the samples were analyzed by Headspace Gas Chromatography. The analysis revealed a decrease in methanol levels at postmortem for all the matrices, except for retina-choroid than its perimortem value. For retina-choroid, no significant change in methanol levels at postmortem was found.

Postmortem redistribution of ketamine in ocular matrices: A study of forensic relevance.

The present study evaluates the postmortem redistribution of ketamine in ocular matrices, such as vitreous humor, aqueous humor, and ocular tissues in an animal model. To understand the redistribution of ketamine and its metabolite (norketamine) in the ocular matrices, an in vivo study was performed in rabbits. The rabbits were divided into two groups: perimortem and postmortem. The postmortem samples were collected at 17 h after the administration of ketamine (40 mg/kg) intravenously. For a better understanding of the metabolism of ketamine in eyes, an ex vivo study was conducted in goat eyes after administration of ketamine intravitreally. The samples were analyzed by LC-MS/MS and the levels of ketamine and norketamine in these matrices were compared with that of whole blood and plasma. The results of the in vivo study showed a decrease in ketamine levels in whole blood and plasma while an increase in ocular matrices at postmortem. Though, in most cases, this increase/decrease was statistically insignificant. Moreover, there was an increase of norketamine level in ocular matrices. Ex vivo study also shows the presence of norketamine in ocular matrices of goat eyes. The presence of norketamine in goat eyes may be indicative of the metabolism of ketamine in the eyes.

Development and validation of an ESI-LC-MS/MS method for simultaneous identification and quantification of 24 analytes of forensic relevance in vitreous humour, whole blood and plasma.

Detection and quantification of drugs from various biological matrices are of immense importance in forensic toxicological analysis. Despite the various reported methods, development of a new method for the detection and quantification of drugs is still an active area of research. However, every method and biological matrix has its own limitation, which further encourage forensic toxicologists to develop new methods and to explore new matrices for the analysis of drugs. In this study, an electrospray ionization-liquid chromatograph-tandem mass spectrometry (ESI-LC-MS/MS) method is developed and validated for simultaneous identification and quantification of 24 drugs of forensic relevance in various body fluids, namely, whole blood, plasma and vitreous humour. The newly developed method has been validated for intra-day and inter-day accuracy, precision, selectivity and sensitivity. Absolute recovery shows a mean of 84.5, 86.2, and 103% in the vitreous humour, whole blood and plasma respectively, which is suitable for the screening procedure. Further, the absolute matrix effect (AME) shows a mean of 105, 96.5, and 109% in the vitreous humour, whole blood and plasma, respectively. In addition, to examine the practical utility of this method, it has been applied for screening of drugs in post-mortem samples of the vitreous humour, whole blood and plasma collected at autopsy from ten cadavers. Experimental results show that the newly developed method is well applicable for screening of analytes in all the three matrices.

Development and validation of a LC-MS/MS method for homocysteine thiolactone in plasma and evaluation of its stability in plasma samples.

The present study demonstrates the development and validation of a sensitive method for the quantification of homocysteine thiolactone (HCTL) in human plasma using the technique of LC-MS/MS. The gradient elution of HCTL was achieved within 5min using ZIC HILIC column having acetonitrile with 0.1% formic acid and water with 0.1% formic acid. The method was validated for the linearity, sensitivity, accuracy, precision, recovery, matrix effect and stability. A good linearity was found within a range of 0.5-32.5nmol/ml. Quantification was performed using multiple reaction monitoring (MRM) mode based on the molecular/fragment ion transitions for HCTL (118/56) and homatropine (276.1/142.2) as internal standard. Generally, HCTL levels in plasma were found to be highly unstable. In order to verify the stability of the HCTL levels in plasma for a longer period, the samples were extracted immediately and stored at -86°C. Using the above method it was found to be stable for a period of 1 month. The method was well applied for quantification of HCTL in plasma of healthy human volunteers.

Regional variation in the levels of macular xanthophylls and carotenoids in dietary components: comparing North and South India.

Multiple epidemiological studies have emphasized the intake of dark green leafy vegetables rich in xanthophylls in reducing the risk of developing age-related macular degeneration (AMD). Therefore, the present study was undertaken to quantify the levels of major carotenoids in commonly consumed fruits and vegetables of Indian origin and of xanthophylls in the macula of Indian human donor eyes. Fresh fruits (n=20) and vegetables (n=51) collected from two zones of India were tested for the estimation of xanthophyll, lycopene and ß-carotene by using HPLC with Photodiode Array Detection. Lutein and zeaxanthin were quantified from macula and in selected vegetables collected from both southern (SI) and northern (NI) regions of India. Xanthophylls, ß-carotene and lycopene were found in many affordable vegetables commonly available for consumption in India. Higher content of lutein and zeaxanthin was confirmed in many economical leafy vegetables and fruits. Surprisingly, the mean macular levels of lutein and zeaxanthin of SI donor eyes (n=13) were found to be significantly (p<0.001) four times less than in NI donor eyes (n=15) and the macular levels of Northern India were comparable with reported levels in western populations. The present study showed considerable levels of xanthophylls in many of the commonly consumed fruit and vegetable sources in both parts of India. However, SI donor eyes showed lower levels as compared to NI donors and this warrants further investigation about the bioavailability of xanthophylls in their blood and food intake. The relevance of these findings with prevalence of AMD in South India needs to be explored.