Sounds like you need to speak to a formulation person in the cosmetics industry!  Basically, whatever is your active ingredient stands to be affected by ANYTHING you use - and using oil in particular would almost certainly change the extract properties, may or may not partition your ingredient between aqueous and oil phases, and could alter its properties.

Basically, the simplest thing to do would be to use a sterile neutral buffer - like phosphate-buffered saline, pH 7.4 - as a starting point, and see what happens to your extract - ie: where does the active ingredient go? Of course, if you want it to penetrate skin, you could think of using dimethyl sulphoxide, which will dissolve most things - but again, what will it do to the active ingredient, and is it SAFE?

As Ed wrote, unless you know the properties of your substance, you must test several options. At first you may try even something that will not be used for the application to skin, just to get some sense of how does it behave. Also, you should probably purify it, at least partially.

we do experiment of medicinally important plant for the isolation of comopound and i think it would be helpful to understand. in order to obtain liquid of your powdered plant you should have to extract it with methanolic and after that portioned methanolic extract with water and hexane to obtained the oily extract from your plant extract. but make sure while using the hexane soluble fraction that it should not contain any traces organic solvents. 

Simply add a dissolving solvent in adequate proportion such as 1mg/ml depending on what you want.

It is an emulsion form, the powdered plant in solid phase and liquid medium that which facilitates the healthy being of the plant content.

In Ayurveda medicines, based on each plant characteristics the liquid medium are

• Water
• Honey
• Oils in some cases.

Most are crystalline but a few are liquid at room temperature. Alkaloids have bitter tastes. The alkaloid quinine for example is one of the most bitter tasting substances known and is significantly bitter at a molar concentration of 1x10-5. Alkaloids are basic natural products occurring primarily in many plants. Alkaioids rank among the most efficient and therapeutically significant plant substances.  Some 5,500 alkaloids are known and they comprise the largest single class of secondary plant substances, which contain one or more Nitrogen atoms, usually in combination as part of a cyclic structure. They exhibit marked physiological activity when administered to animals. Alkaloids are often toxic to man and many have dramatic physiological activities, hence their wide use in medicine for the development of drugs. Pure, isolated plant alkaloids and their synthetic derivatives are used as basic medicinal agents for their analgesic, antispasmodiac and bactericidal effects. Quinine with a molecular formula of C20H24N2O2 is an anti-malarial drug extracted from the bark of a cinchona tree (C. succirubra). Quinine is highly valued in the treatment of unusually resistant strains of malaria. 

http://shodhganga.inflibnet.ac.in/bitstream/10603/1026/7/07_chapter%202.pdf

Ms. Ellie Mjor

To the above list of Krishnan, I would like to add butter/ghee which are biologically and environmentally safe as they are widely used as food ingredients to prepare a paste that can be applied on the skin. You can also think of Aloe vera gel which in itself is good for the skin as an additive. Paste of turmeric powder prepared with water is widely used in India in ceremonies, functions and festivals, as a skin cosmetic and is applied on the entire body especially by ladies.

Good luck.

Take the dried powdered plant material in an appropriated sized vassal (preferably glass) and pour a suitable extractant (Organic solvents, Alcohol, Water, etc) over, completely covering the herbal material. To ensure complete extraction, addition of more extractant over the next day or two will be required. A good ratio for dried material is about 1 part herb to 5 parts extractant and with fresh material 1 part herb to 3 parts alcohol. Cover with tight fitting lid and be sure to place a plastic bag sandwiched between the lid and the jar. Shake well and place the jar in a dark place & allow the herbs to soak or macerate for 2-3 days. Occasional shaking will facilitate the extraction. The extractant will siphon and extract the active constituents from the herbs. When the extraction is complete, filter the material and collect the solvent extract in separate vessel. You can concentrate the extract so obtained by distillation or evaporation. The extract left over is saturated, is the strongest in terms of active medicinal constituents. Store this concentrated extract in smaller bottles, preferably amber bottles in a cool dark place. Water extracts however cannot be stored for long. In this case you should completely remove the water while will yield crude extract as solid mass containing bioactive chemical constituents of the plant material.

Powder from the plant extract may either they are not dissolve in oil or  in water. In order to dissolve the powder material, we can use DMSO (dimethyl suylfoxide), tween 80 and some organic solvents.  First we should take required amount of powder material and add some dissolving agents (desired quantity) into it. Stir or mix well and we can increase the volume by adding water in it. DMSO is the best option for dissolving the powder material if the solution will be used for health related treatment. For insecticidal use we can use Tween 80 and some organic solvents. These dissolving agents will not diminish the quality of the plant material.

I too agree with the Aloe vera gel and turmeric inclusion as they have been already time tested for topical use. You can instead use olive oil or jojoba oil as you say for the purpose. Just test the solubility of your compound or extract in the vehicle and find out analytically (might be spectroscopically or by HPLC) how much is available in the final solution (in %). Report that percentage on your label and go ahead. Most of the marketed products are being sold like this only. 

Ms. Ellie Major

The use of any solvent to prepare an extract or to extract phytochemicals from your plant material, will modify/transform the physical, chemical, biological and medicinal properties of your product,  sometimes markedly. Is this what you want?

Please add requisite solvent as you wish to prepare a required concentration (eg. w/v).

Basically, you have to answer two questions.  First: are your active constituents predominantly hydrophilic (water-soluble) or hydrophobic (oil soluble)?  Like dissolves like; keep that in mind.

If you want to dissolve both kinds of compounds into your menstruum, then you need a mixture of solutes, or a solute that is not super-polar or super nonpolar. 

Your second question is, what do you intend to use it for?  If it's meant to be a topical cream, you're obviously going to want to consider different solvents than if it is meant to be ingested.

Sorry to make this not a simple answer, but what you really need is a book on herbal medicine-making in order to guide you in terms of what is best for which plant you have.  Try Green's The Herbal Medicine-Maker's Handbook or Cech's Making Plant Medicine for the down-and-dirty details.  They are both layman's guides, and have their quirks, but their information is reliable for this kind of work.

If you're attempting to sort a study that you eventually intend to publish, I suggest going to pubmed and searching for the title of your plant (in Latin, with quotation marks) and looking at free articles' Materials and Methods section to see how they prepared their sample.  Often, it gets rather complex, so it's best to go straight to other people who intend to do the same thing you do.

Good luck!

-JS

The most common means of making herbal liquid extracts (referred to as tinctures) is with a process known as maceration. When herbs are soaked (macerated) in a solvent made of a mixture of water and alcohol (ethanol), the extraction process stops when the concentration of a compound in the solvent equals the concentration remaining in the extracted herb (equilibrium), known as the marc. Relatively complete extraction of certain components in the herb can only occur under these conditions if the amount of solvent is great and little herb is used, resulting in an extract that is extremely weak. Even this will only occur if the compounds in the herb are completely soluble in the ratio of water to alcohol used. When using a water/alcohol mixture as the extracting solvent, a complete solubility, and therefore extraction, does not occur for any single compound, much less all of the components simultaneously.

There are many ways to prepare herbal extracts. Herbal tinctures are simply herbs extracted with alcohol, glycerin, or vinegar. In traditional herbal medicine systems, herbal remedies are prepared in several rather standardized ways which usually vary based upon the plant utilized, and sometimes, what condition is being treated. Some of these methods include: infusions (hot teas), decoctions (boiled teas), tinctures (alcohol and water extracts), and macerations (cold-soaking). Following threads may provide you related information:-

http://movelikeagardener.com/how-to-prepare-plant-medicines/

http://www.rain-tree.com/prepmethod.htm#.VOQ0heaUckU

http://www.wikihow.com/Make-an-Herbal-Tincture

I agree with Dr. Jaime Seltzer's opinion.

It is easy to prepared extract BUT very difficult to prepare extract of the interest. One should know about major and minor chemical constituents rather class of constituents, which helps in selecting the solvent. Further, one must be clear about phyto-marker and bio-marker of desire interest.  Many-a-times, some minor constituent proves responsible for the efficacy of the herb.

It is always better to keep in touch with chemist and pharmacologist from planning of certain studies.

You can use solvents of varying polarity for making herbal extract in solutions.And the use of solvents depends on the nature of chemical constituents needed for your studies. ie less polar to high polar compounds can be fractionated in different solvent s and in their combinations.

Prepare aqueous cream base and then add your extract prepared in concentrated form 

Hey Ellie,

I found your question when I was looking for the solution myself. I'm not sure if you're still interested in this but I found some answers and some work that addresses this. Turns out those extracted powders don't serve much or any use topically, rather the more cost effective solution in terms of both time and money, is to use essential oils. This is especially true if you don't want to add water to the solution, you can always use polysorbate 20 or 80 and other solubilizers. The powders and herbs are generally used for oral consumption (think capsules, teas, coffee, etc.)or as poultices. 

Moreover, the method or alcohol extraction is often seen as time consuming and counterproductive due to the doubling up process of extraction and also due to the fact that alcohol hands down will preserve most of the plant properties anyway, or the most out of the commonly used methodologies. There are some glycerite extraction processes that are a thing but I can't find the literature on them unfortunately, I can only surmise that it's a large scale operation, or an expensive one. 

You can also create or extract most of the plant chemical compounds needed for topical creams as most medications do and then emulsify them via elusion or using a surfactant. Here are some cool things I found in terms of research here:Article Essential Oils and Herbal Extracts as Antimicrobial Agents i...

and here

https://www.omicsonline.org/open-access/a-review-on-the-extraction-methods-use-in-medicinal-plants-principle-strength-and-limitation-2167-0412-1000196.php?aid=58448

also Wikipedia explained this stuff in detail over here  https://en.wikipedia.org/wiki/Topical_medication

Hope this helped!