Recommended Practices in Essential Oil Research

Transcription

1 Recommended Practices in Essential Oil Research 47th ISEO, Nice September 11-14th, 2016 Alain Chaintreau Flavour and Fragrance Journal

2 Quantification 2

3 Frequent bad practices Composition in MS area % Composition in MS area % MS response is not stable MS% should never be used Composition in FID areas % Response factors (RRFs) are stable Over 6 months: D(RRF) < 7% And over > 30 years! But FID% are inaccurate up to 26% error Area% and semi-quantification are unreliable 3

4 Good Quantification Practices GC-FID or GC-MS GC-FID Experimental calibration Accurate Time consuming building calibration curves or determining RRFs Requires all pure standards Or standards with the same molecular formula Only way in MS Recommended IOFI Practice Flavour Fragr. J. 2012, 27, Predicted response factors Prediction from only the molecular formula No need of authentic substances Mean accuracy 6% Almost as rapid as semi quantification (RRFs = 1) Recommended IOFI Practice Flavour Fragr. J. 2016, 31,

5 Comparisons of approaches Ful Internal standardization Accurate Time consuming Predicted RRFs Close to internal standardiztn Rapid Extremely simple Determined only from the molecular formula Calculation sheet in open access (Supplementary material to [Flavour Fragr. J. 2012, 27, ]) Composition of a bergamot EO Compound Internal Standard Predict. RRFs RRF =1 b-pinene p-cymene Limonene g-terpinene Linalool Octyl acetate Linalyl acetate Geranyl acetate a-bergamotene Oxyg.cpds/terpenes Sum of masses (mg) Global recovery Experimental time 2 days 3 h 2 h From [Flavour Fragr. J. 2012, 27, ] «Semi-quantification» or FID% Overevaluation of terpenes Underevaluation of oxygenated cpds Wrong ratio oxyg.cpds/terpenes Wrong total mass & recovery But very short RRFs Semi-quantification should not be used anymore 5

6 E.O. Sampling for quantification Direct EO injection with a syringe Most representative way Simultaneous distillation-extraction (SDE) Close to EO composition Headspace Partition EO/HS biased Direct SPME from a distillate Partition Distillate/fiber biased HS-SPME from plants 2 Partitions: Plant/HS and HS/fiber biased Composition (%) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Recoveries from an aqueous solution (4 constituents at 25%) Real composition SDE D-SPME HS-SPME P&T-HS Vanillin 2-propanone 2-phenylethanol pyridine SPME (and stir-bars) never representative of an EO 6

7 Quantification of regulated F&F substances Because it deals with health issues, the method reliability must be known Purity of standards NMR with internal standard, GC & predicted RRFs. FID% not valid Basic principle for multi-analyte quantification The analyte identity must be checked in the quantification run [Official journal of the European Communities, 2002, L221 (2002/657/EC)] Validation is part of a quantitative method development Most reliable approach: accuracy profile LOQs, Method linearity, Tolerance intervals at a given confidence level Full details in press [Good quantification practices of flavours and fragrances by mass spectrometry, F Begnaud, A. Chaintreau; Phil.Trans. A, in press] 7

8 Writing a research paper 8

9 Introduction and novelty The author(s) should have an exhaustive knowledge of the bibliography related to the topic Most relevant papers to be commented in the introduction From this knowledge, describe what are the innovative points in the proposed work Optimization is not novelty does not justify a publication A. Chaintreau, 47th ISEO, Nice, 9 September 11-14th, 2016

10 Experimental section Overal objective Raw materials (Chemicals and plants) Give enough information for others to repeat the experiments Give their origins Wild plant authentication by a botanist Measure the moisture content prior to distillation. Enough "biomass" amount to accurately weight the resulting EO New techniques To be described in details Known methods Refer to adequate publications Statistical analyses To be clearly described with references to the methodology used 10

11 Identification / quantification See previous slides by D. Joulain and A. Chaintreau Variability of quantities to be reported Replicated GC injections not valid Perform replicates starting from different sample batches 11

12 Synthesis Yield From the isolated compound Structure and purity By NMR (Purity using an internal standard) Retention index (If volatile) On usual GC phases Organoleptic properties Report the descriptors Use a panel 12

13 Sensory analysis Informal sensory evaluation not valid Use a panel and recognized tests (e.g. ISO, ASTM): Triangle test: ISO 4120 Quantitative descriptive analysis ISO 13299, ISO Paired comparison ISO 5495 Odor thresholds ISO Etc. 13

14 GC-Olfactometry Evaluation with 1 or 2 panelist(s): not valid Subject to specific anosmia and over-sensitivity Use a panel and a recognized technique AEDA CHARM with a panel GC-SNIF (=detection frequency) OSME or FSCM (panel to be trained) 14

15 Bioactives I (G. Buchbauer) EO Characterisation Exact definition of the EO (chemotype, subspecies, etc) Correct analysis of main constituents (because responsible for the bioactive reaction) see the identification/quantification section Statistics Run comparisons with the blank, a placebo, a positive and negative control Run a comparison with a medicament in use Methods Use several & up-to date methods for a given bioactivity study E.g. when dealing with antibacterial, then at least Gram-+ and Gram- - Test the complete EO and its major constituents Test several bioactivities Antioxidant property only is not sufficient, even if this has been carried out with a rare and seldom plant-eo. 15

16 Bioactives II (G. Buchbauer) Traditional medicine Confirm bioactivity of folk medicine by modern test methods Experiments with the main or with the major two-three constituents The main constituent is always responsible for the effect. A complementary activity is positive (a concomitant use with a medicament) Bioactivity mechanism to be investigated, or present experiments in this direction. Prefer rarely investigated bioactivities e.g. plant-plant-intercommunications, or plant-pollinators-intercommunication, or plant-pollinatorsintercommunications, or pheromones, or interactions against allergies, or against diseases as malaria, or against viruses (not always herpes simplex I and HS II!), or against diseases caused by other animals (snakes, snails, worms, other parasites, etc). Here often bioactivities documented in folk medicine (e.g. snake-bite, is there really a success or not). Pitfall examples see D. Davenne s presentation 16

17 Reviews Only authored by experts, able to judge existing papers The review must be critical 17

18 Ethics Plagiat New software allow detecting the «copy and paste» sections coming from previously published papers Plagiat is subject to legal actions Animal and human testing Animals permission of an authoritative office or commission (university or labor) Humans (invasive expts, e.g. blood taking) permission of an ethic commission.

19 URL links to recommended practices (free access) Flavour and Fragrance Journal Full texts on the ISEO web site GC quantification LC MS identification of flavouring substances in nature Solid-phase micro-extraction (SPME) of volatile flavour compounds GC/MS quantification with selected-ion monitoring (SIM) Simultaneous distillation-extraction (SDE) Rapid quantification using GC-FID and predicted relative-response factors Philosophical Transactions A Good quantification practices of F&F by MS Phil. Tran. A. In press, released Sept. 19th European Directive Performance of analytical methods and interpretation of results 19

20 Thank you for your attention