What is Citriodiol®?
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Citriodiol® is nature’s most effective insect repellent. It is produced from eucalyptus citriodora oil using a process which mimics that which naturally occurs in the leaf by converting citronellal into p-menthane-3,8-diol. Citriodiol® is a standardised preparation containing isomers of p-menthane-3,8-diol (PMD) and small amounts of related products.
Typically, Citriodiol® contains 64% PMD (a mixture of the cis and trans isomers of p-menthane-3,8-diol). Citriodiol® has been notified under the European Biocidal Products Directive (BPD) 98/8/EC and is currently proceeding through the registration process with the Heath and Safety Executive in the UK. It is the only naturally sourced ingredient that can now be used as an insect repellent.
It is notified as 'a mixture of cis and trans p-menthane-3,8 diol / Citriodiol®'. EC Number 255-9537 • CAS Number 42822-86-6. Because this is also the CAS Number for Citriodiol®’s main constituent, PMD, the American Chemistry Association has now assigned Citriodiol®, described as “oils, eucalyptus, E. citriodora, hydrolyzed, cyclized” a unique CAS Number 1245629-80-4. The appropriate CAS Number to use for product registrations will vary by territory, so please check with us before making your submission.
The major components of Citriodiol®
The major components of Citriodiol® are racemic cis-and trans-p-menthane-3,8-diols and two minor isomers, PMD3 and PMD4.
The isomers are all racemic, i.e. they are composed of equal amounts of the (+) and (-) isomers (Nishimura et al, 1984, Barase et al, 2002). All four major PMD isomers, (+)-cis-, (-)-cis-, (+)-trans and (-)-trans show comparable insect repellency (Barasa et al, 2002) Citriodiol® contains a minimum of 64% PMD.
The minor components of Citriodiol®
The minor components in eucalyptus citriodora oil, which amount to 25%, are unaffected by the mild acid environment used to convert citronellal into p-menthane-3,8-diols. Eucalyptus citriodora oil (75% citronellal) gives Citriodiol® (64-70% p-menthane-3,8-diols) and the apparent loss of product is accounted for as follows:-
a) Some citronellal is cyclised with dehydration, leading to isopulegol isomers which are already present in the eucalyptus citriodora oil.
b) Some of the p-menthane-3,8-diol reacts with the citronellal to give acetals.
The identity of the other minor components in eucalyptus citriodora oil and hence in Citriodiol® is somewhat dependent on the country of origin of the starting material. Citrefine International Limited obtains eucalyptus citriodora oil from only a handful of established sources to ensure the highest quality of oil and better monitor the social and environmental practices at each plantation.