by Eric Brand

The natural concentration ratio of single medicinals can vary significantly from item to item. Items with more water-soluble constituents naturally tend to produce lower concentration ratios; these items are often sticky fruits such as Da Zao (Jujubae Fructus) or starchy substances such as Shan Yao (Dioscoreae Rhizoma). By contrast, many vine and stem products have a high crude weight relative to their water-soluble constituents, so they can often achieve very high concentration ratios. Examples include fibrous products such as Zhu Ru (Bumbusae Caulis in Taenia), Ji Xue Teng (Spatholobi Caulis), and Ren Dong Teng (Lonicerae Caulis).

Beyond the quantity of water-soluble constituents within a given medicinal, the characteristics of the constituents themselves affects the final concentration that can be achieved. Items that produce an extract that is naturally sticky or oily tend to require more excipient to prevent clumping, so these items tend to have a lower concentration ratio. Examples of such substances include Dang Gui (Angelicae Sinensis Radix) and Gou Qi Zi (Lycii Fructus).

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Additionally, the quantity of water is important. As a basic rule of thumb, the herbs should have enough space in the decocting vessel so that water can circulate effectively. If the vessel is too densely packed with herbs or if the herbs are not sliced effectively to maximize their surface area, the extract is not efficient. To avoid this problem, good manufacturers conduct tests with varying quantities of water and raw herb materials in order to identify the optimal conditions for extraction.

Cooking time also affects the concentration ratio of a given preparation. At a minimum, the cooking time should meet or exceed the cooking time that is indicated for a traditional stovetop decoction. Cooking for prolonged periods of time tends to produce a more complete extract, and cooking the herbs a second time after the first batch of water is saturated will result in even more extract material (this tends to lower the concentration ratio because more extract is produced from the same starting material).

The question of what constituents a “complete extract” or an “optimal extract” is challenging to answer. Some items appear to have active constituents that are best extracted with prolonged cooking. Other items are best with a shorter decoction time. Different companies research the ideal circumstances for each medicinal, but at the end of the day there is not absolute consensus on this issue, and little data is shared between companies.

If the overall decoction time is shorter, the yield tends to be somewhat lower. If the decoction time is prolonged or if the herbs are cooked for a second time, more extract is created and the yield is higher. Thus, if ten kilograms of crude medicinals are cooked at a peak temperature for three hours and the resulting yield is one kilogram of dried extract, we say that this is a 10:1 concentration. If the same ten kilograms of raw material was cooked for ten hours with two batches of fresh water, the yield could be two kilograms of dried extract, creating a 5:1 concentration. Which is better?

Ultimately, in the example above, it is likely that there is not any one “right” answer across the board- it probably varies from substance to substance. Without question, it is essential that the extraction process replicates a traditional decoction. It would be ridiculous to cook the herbs for only five minutes before straining and drying the decoction, but in theory such a process would create very little extract relative to the raw herbs (the source-to-product ratio could be 100:1 or more). However, it would also be unnatural to decoct herbs for two days with several changes of water because such a process is not consistent with the standard decoction process of Chinese medicine.

When it comes to extracts, it is not about “getting as little out as possible” or “getting as much out as possible.” There should be a balance between extremes that reflects the traditional decoction process. If the extraction is too inefficient, it is a waste of raw materials and it will result in a product that lacks clinical efficacy. On the other hand, if the extraction process is much more prolonged than a traditional decoction, the concentration ratio could be unnecessarily low, resulting in more profit for the manufacturer but less concentrated medicine for the consumer. Thus, the art is to mimic what should come out in a traditional decoction.

To use a familiar analogy, think about espresso coffee. Espresso connoisseurs prefer a relatively “short pull,” meaning that they stop the shot before it is complete. The shorter exposure to steam rushing through the coffee results in a shot that is shorter and more concentrated, and it produces brown foam at the top of the shot called “crema.” If more steam moves through the ground coffee, it will produce a larger shot that has more liquid and more solute but lacks the delicate “crema.” If one dried out the espresso from a short pull vs. a long pull, the two pulls would have different concentration ratios because the longer pull will have more dissolved solids (solute).

If the short shot of espresso was dried and turned into an extract powder, we may find that a ten gram serving of ground coffee yielded one gram of dried powder after being made into a “short shot” of espresso. This would be a 10:1 concentrate. The same coffee extracted with a “long shot” of espresso might yield a 7:1 concentrate, because more extract was created. Boiling the ground coffee in water for hours might yield even more extract, perhaps bringing the concentration down to 5:1. Which product would make the best instant coffee? With coffee, the short shot would probably have the richest flavor, but the cost per kilogram would be higher than the other batches because of the comparatively low yield.

Now, if Chinese herbs were as straightforward as coffee, it would be easy. Since coffee is only a single substance, it is likely that one could find the best way to extract it to maximize its flavor, value, and potency. However, each given Chinese herb has complex needs just like coffee does, and the process that is ideal for one herb may not be the best for another herb. Some herbs nearly certainly have delicate “crema” while others are probably best done by cooking them for hours and hours.

At present, there is a tremendous amount of scientific research that goes into determining optimal extraction ratios, but most of the research is done in the private sector. There is relatively little published data from neutral sources, so most of the current science remains in the realm of closely guarded trade secrets. Each manufacturer claims to have the best approach, yet each manufacturer also has the flexibility to accommodate large OEM orders that meet different specifications than their house standard.

Large-scale studies that measure levels of marker compounds would represent one of the most valid methods of evaluating manufacturer’s claims, yet these studies have generally not been conducted on any comprehensive scale. Furthermore, if marker compounds were used as research standards to evaluate the quality of various products, the industry fears that the trend would create a strong incentive for manufacturers to manipulate their testing results by adding in fractional isolates of the marker compounds in order to make their products appear superior.

Consequently, there is no final word on which techniques are inherently best. Given the diversity of manufacturing methods, the varying needs of hundreds of disparate medicinals, and the inherent natural variations in plant chemistry, it is likely that there is no “one size fits all” solution to the question of concentration ratios. Rather than seeking out a single correct answer, it is important to understand the various issues involved, and the various perspectives found across the industry.

Taiwan

In Taiwan, both single extracts and formula extracts are produced at variable concentration ratios. The main prescription style in Taiwan can be regarded as a new direction in the field of Chinese medicine because it relies on combining whole formulas rather than building a formula based on single herbs. This style, along with the fact that the national insurance system in Taiwan caps the total prescribed daily dosage, has given Taiwan a new method of formulation that does not depend on converting granule weight to its raw herb equivalent. While this prescription style is an inherently valid, experience-based, and time-tested approach to using granules, few Western practitioners have been adequately exposed to this method of use.

As most TCM doctors in Taiwan do not use concentration ratios as their primary means of determining dosage, the Taiwanese domestic market tends not to use excipients to create even concentration ratios across the board. While the majority of products in Taiwan consistently contain 50% starch, the concentration ratio of the extract portion can vary widely from one brand to the next. In fact, sometimes there is close to a two-fold difference in the concentration ratio of the same product produced by two different suppliers.

This feature makes calculation to raw herb dose weights highly individualized from product-to-product, since one product may be 3.2:1 while the next may be 4.7:1. While computerized systems for precise dosage calculation could be easily implemented with these products, there is a lot of variability from brand-to-brand and sometimes even batch-to-batch. Since practitioners in Taiwan rarely use granules based on a raw herb conversion factor and the ratios are rarely provided on the U.S. labels for these products, few systems have been created to allow for easy dosage calculation based on raw herb equivalence with Taiwanese granule products.

Mainland China

As mentioned above, in mainland China it is common for manufacturers to produce most products at variable concentrations initially, and then the products are mixed with excipients to create an even concentration ratio (5:1 is the most common). This specification largely comes from market pressure to produce a consistent product that can be easily converted to its raw herb equivalent.

One common method used in mainland China to achieve this consistency is to add excipients in order to dilute the more potent extracts to an even 5:1 concentration. For items that naturally achieve concentrations that are lower than 5:1, the cooking time and other factors can be adjusted so that the yield is lower, or the product can just be naturally produced at 3:1 or a different concentration ratio. Some suppliers disclose these exceptions, others do not. At the time of this writing, full disclosure remains an issue with many manufacturers, in mainland China and Taiwan alike.

Whole Formulas vs. Singles

When producing whole formulas rather than single extracts, it is often much easier to create products with an even concentration ratio. While single herb extracts can vary dramatically in their concentration ratios, often things even out when a compound formula is decocted together.

Unlike single herbs, whole formulas are commonly made into prepared pill products such as gelatin capsules and tablets. Clumping is not an issue with tablets and capsules, so formulas sold in pill form can often achieve higher concentrations than formulas sold as a loose granule powder.

It is not uncommon to see tablet preparations that reach relatively high concentration ratios, such as 7:1. Pure extract powder packed into gelatin capsules can reach even higher concentrations. However, many products on the market that are sold in a capsule or tablet form do not contain any information on their concentration ratios, and some suppliers simply grind up raw herbs for use in pill products.

In response to the widespread problem of prepared medicines that lack labeling information on their concentration ratios, many manufacturers have begun to produce products that have a consistent, openly-stated concentration ratio. It can be challenging for practitioners to dose prepared medicines if each remedy varies significantly in its potency, so it is common for manufacturers to keep an entire line to a consistent standard concentration ratio (5:1, 7:1, etc).

In order to produce formulas at a consistent concentration ratio, it is often necessary to research the appropriate cooking time. For some formulas, boiling the decoction in water for just two hours may produce an 8:1 concentrate, while other formulas may need to be boiled for much longer to yield an 8:1 concentrate.

Generally speaking, the precise details of many manufacturing techniques are regarded as trade secrets. Despite the widespread use of granules, there is relatively little literature available to guide practitioners in issues such as concentration ratios, dosage, and clinical use. Clinicians largely learn to prescribe granules from watching their teachers, and most of the people that have true expertise in manufacturing are biased by ties to private industry. A blog such as this one is based on visiting many factories and speaking with experts in manufacturing and quality control, as well as interviewing numerous clinicians and observing prescription trends in Taiwan, mainland China, Hong Kong, and the USA. The field of granules is constantly evolving and replete with questions that are difficult to definitively answer, and our understanding is constantly being refined by feedback from other experts.

At Blue Poppy, you can trust that informed experts are constantly evaluating variables such as the ones raised in this blog series. Our products are produced based on replicating the complete traditional decoction process, and we do not cut corners at any stage. From raw material sourcing to optimized extraction procedures, we are there to ensure that you have the finest medicine available for your patients. We are proud to offer the most transparency and the most extensive third-party testing in the industry, and we welcome you to join us in pioneering the future of Chinese medicine.