HPLC Analysis of Garlic

HPLC Analysis of Garlic Clove Homogenates (continued)

Component	Source of Variation	Sum of Squares	Degrees of Freedom	Mean Squares	F	P-value

Allyl	Between Groups	50.54	2	25.27	1.4	0.276
	Within Groups	269.66	15	17.98
	Total	320.2	17

1-Propenyl	Between Groups	87.57	2	43.78	59.13	7.68E-08
	Within Groups	11.11	15	0.74
	Total	98.68	17

Methyl	Between Groups	67.21	2	33.6	2.03	0.165
	Within Groups	248.02	15	16.53
	Total	315.23	17

Table 5. Analysis of variance

Whilst the differences in primary flavour compounds between isozyme groups appear limited to the effect of the initial level of the 1-propenyl cysteine sulphoxide in intact garlic tissue, the relationships between common morphological characteristics and between morphological characteristics and alkyl groups (derived from alkyl cysteine sulphoxides) appear more evident. Tables 6 - 10 show the calculated correlation coefficients ( r ) for all available features of the samples (Table 4) and whilst a number of significant correlations can be seen, relationships of this nature in plants are seldom linear and so the figures should be viewed with caution until further studies have been undertaken. It is worth noting at this point that Saghir has reported on the use of chemical and anatomical data as valuable indicators of taxonomic relationships in alliums and has suggested a correlation between the proportions of alkyl sulphides found in tissue samples and morphological features such as inflorescence and bulb structure and leaf anatomy.

Conclusions

From a practical standpoint there were some elements of the method that require close attention and possibly some modification,

samples for HPLC injection must be totally dry as water contamination causes severe ‘spiking’ of the traces,
the pre-guard filter must be cleaned in 20% nitric acid in an ultrasonic bath for 30 minutes every day. Such is the level of deposit that failure to clean (or replace) this filter regularly causes increasing back pressure and drifting retention times,
because of the solvents employed, only glass syringes should be used for HPLC injection and,
whilst every effort was made to ensure consistent final sample volume this method can inherently lead to error at this stage.

The tests have shown that there is a significant difference between the levels of some primary flavour compounds found in garlic tissue homogenates and some principal isozyme groups.
There was an insufficient number of representative samples from secondary isozyme groups to enable statistical analysis beyond the primary groups. A representative from primary isozyme group 2 would aid future investigations.
Whilst every effort was made to confirm the identities of the clones used, future studies should include isozyme testing as an accurate means of grouping.

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