Fluid Extracts
Fluid extracts are alcoholic extracts with a weight:volume ratio of 1:1. The alcohol content is usually the same as for tinctures although, curiously, sometimes lower in commercial production. They are really nothing more than concentrated tinctures. One confusing modern feature is the appearance of extracts (e.g., of Ginkgo leaf, Ginkgo biloba) in which a much higher wt:vol ratio such as 10:1 or more is achieved by industrial process. These are still referred to as fluid extracts, although unimaginable to those who first devised the term. Originally tinctures were produced by maceration and fluid extracts by cold percolation – the appeal of a 1:1 product, easily achieved by the percolation process, is that in theory 1ml of tincture should be equivalent therapeutically to taking 1g of the dried herb.
USES
Logically a 1:1 fluid extract should be five times stronger therapeutically than a 1:5 tincture; in practice this is seldom the case – and may be more than five times as expensive. Nevertheless, fluid extracts have their uses because they are more compact.
There are a small number of herbal remedies that must be employed in high doses to achieve a drug-like action from a relatively mild herb, and in this role would often require an unmanageably large volume if dosed in tincture form. As fluid extracts are so much more condensed, a more convenient dose range is possible.
A common problem is the need to use several remedies in a mixture, with the attendant conundrum as to whether one should in consequence accept relatively weak actions from the standard 100ml per week dosage, or whether to increase the dose and therefore the cost and inconvenience. Canny practitioners will often opt to carry a small range of fluid extracts that they are accustomed to dosing generously and are therapeutically viable as extracts, and perhaps not overly expensive; in this more condensed form one has effectively “made more room in the bottle” for other remedies. Popular choices may include Dandelion root, Taraxacum officinalis, Liquorice Root, Glycyrrhiza glabra, White Willow bark, Salix alba, and Valerian root, Valeriana officinalis.
METHOD
One may still find in antique shops the hand-blown glass percolation funnels once used to make fluid extracts by allowing menstruum to trickle slowly through a column of the powdered herb. This required patience and very considerable expertise, which must really be abandoned, however wistfully, as a technology of a bygone age. At least one commercial manufacturer has adapted the process by percolating ordinary “cut & dried” herbs in huge stainless steel percolating vessels, with acceptable results; confusingly, they also produce most of their “tinctures” by the same process. See Percolation
Repeat maceration
An excellent method, popular commercially and, of greater significance, viable in small-scale production, is repeat maceration. To explain, if one macerates 250g of herb in 1 litre of menstruum, the result will be approx. 1 litre of 1:4 tincture. Use this tincture to macerate a further 250g of herb, to yield a 1:2 result. Repeat twice more, and you have arrived at a 1:1 extract. Bear in mind that if using dried herbs there will be a loss of fluid at each pressing. One must allow for this by reducing the quantity of herb at each successive maceration so that the menstruum will still “cover”. The final yield may be as little as 60% of the original volume depending on the efficiency of the press employed.
A useful compromise may be to repeat the maceration less often to yield, say, a 1:2 result. Of course a 1:1 extract can be derived from re-macerating only once or twice respectively if the starting point is a 1:2 or 1:3 tincture, as should be the case with dense dried herbs and most fresh herbs of all sorts. Note that in the case of extracts made from fresh herbs it may well be necessary to increase the alcohol content slightly to compensate for accumulated water content.
It is also common practice to “recycle” any surplus tincture remaining from a previous year’s production by incorporating it in the menstruum of a fresh batch (particularly when using fresh herbs).
There is no good reason why not provided it is understood that a more concentrated product will result, allowed for in subsequent prescribing.
A sort of fluid extract of Liquorice root, Glycyrrhiza glabra can be produced by dissolving the Liquorice juice sticks or blocks (solid extracts) available from some herb suppliers, to saturation point in 25% alcohol.
Percolation Method
Use a standard 1:5 weight to volume ration but increase the volume of alcohol by 20%. If the herb is normally extracted using 50% alcohol, this means increasing the percentage of alcohol to 70%. The added alcohol makes up for the water that will be added later in the process.
Set up the percolation and allow the equivalent of 75% of the weight of the herb to percolate through. If you used 100 grams of herb, you would allow 75 milliliters to percolate through; if you used 10 oz of herb, that would be 7.5 fluid ounces. Set this liquid aside.
Continue percolating the remaining menstruum, then loosen the cap on the percolation cone and flush the marc with boiling hot water. Transfer the remaining percolated menstruum and the water to a shallow pan and evaporate in a food dehydrator or in an oven on low heat until the liquid is reduced to 25% of the volume of herb. Using the above examples, that’s 25 milliliters or 2.5 fluid ounces. Combine the 25% reduction with the 75% percolated menstruum that you set aside earlier. You now have a 1:2 fluid extract.
Mixed Extract
Another variation on the theme worthy of mention in this section is the mixed extract. One becomes accustomed to dispensing two herbs with very similar actions because of their symbiotic affinity – it soon occurs that if a tincture of one is used as the menstruum for the other, one will once again have “saved room in the bottle” when prescribing. Suitable combinations might include Saw Palmetto berries, Serenoa serrulata with Nettle root, Urtica dioica, and Sea Holly, Eryngium maritinum with Gravel root, Eupatorium purpureum. One may also take the opportunity to combine different parts of the same plant harvested at different seasons, thus to combine the autumn berries and spring flowering tops of Hawthorn, Crataegus oxycanthoides, or the summer leaf & autumn root of Parsley, Petroselinum crispum.
For an in-house production of extracts it will occur sooner or later that as one proceeds through a repeat maceration process, an increasing amount of the active constituents remains in the “spent” marc, which seems a waste. There is no reason why this partially spent marc should not be re-macerated and the resulting weak tincture used as the starting point for the next-up-in-strength, and so on. This is a variant of serial maceration. As the results would be very difficult to calculate one relies on tasting work in progress until a product of recognizable strength has been achieved. It would mean, of course, having one or two batches of a given herb on the go indefinitely.