Scientific evidence for synergy in a botanical product

So, you’re curious about herbal medicine. Is there any truth to this stuff?

Uncle Howie tells you that he read in the National Enquirer about an herb that has better antibacterial effects on cuts and scrapes than Neosporin ointment — never mind that Neosporin is composed of three different antibiotics that come originally from bacteria themselves.

So you set out on a quest to purchase some of this herb, known colloquially as goldenseal. When you go to your local Whole Hippie Dump-a-Load-of-Cash Emporium you find goldenseal alright, in about twenty different forms. On one side of the aisle are containers with loose, crushed up leaves and roots that look like medical marijuana. On a shelf, you find see-through capsules that seem to contain a powdered version of the herb. Down the aisle a bit you find boxes of blister-packs containing a proprietary extract of free-range goldenseal from the Appalachians harvested under moonlight by bare-breasted virgins. The same company also makes an ointment, allegedly procured the same way.

A scraggly young man with a rainbow-colored Whole Hippie tam comes by and says, “Dude, can I help you?” As you wave away the cloud of patchouli oil and three days of body odor, you ask him, “So, this goldenseal — which one should I buy?”

Hippie Boy looks both ways down the aisle and motions with his finger to come close.

“Dude, all this expensive stuff is just a ploy by The Man trying to make a buck with their fancy scientific words and processes. What you want is the whole herb, man — the stuff given to us by the sprites and spirits. Those capsules miss the point. Part of the magic is missing. You pay extra to get less.”

“But, dude,” you say. “I want to try the ointment, you know, for cuts and scrapes. How do I use this herb?”

The fine young man then explains how to make a poultice, an old-fashioned decoction of plant material that one wraps on a cut — sort of like collard greens.

This really seems like more trouble than it’s worth. You’re about a millisecond away from just heading down to the Done-Rite Drugs, Liquor, and Tobacco to buy a simple tube of Neosporin. But hey, it’s an experiment and you’re curious.

While you’re checking out from the health food store, a local scientist friend is in line at the next register, checking out your stash of goldenseal.

“You know, you should really go read Science-Based Medicine to get the straight dope on that stuff.”

And so, here you are. And I’m here for you.

[Note to readers: Apologies to my hippie friends. I love you all. No hippies were harmed in the drafting of this blogpost.]

Is there any scientific evidence to support a common herbalist claim that whole plant materials are “better” than semi-purified extracts or pure, individual chemicals made by the plant?

And I can tell you this — it depends.

ResearchBlogging.orgBut as long as the National Center for Complementary and Alternative Medicine (NCCAM) is in existence, this is the exactly the kind of work that should be supported by this arm of the US National Institutes of Health. In a recent paper to appear in the Journal of Natural Products, Dr. Nadja Cech and colleagues from the University of North Carolina at Greensboro, Dept. of Chemistry & Biochemistry, used traditional separation chemistry and cutting-edge analytical chemistry techniques to address this very question.

[Update: I neglected to note at the time of posting that Catherine M. Cooney wrote a nice article on this work at the online site for Chemical & Engineering News.]

The medicinal use of goldenseal (Hydrastis canadensis L. (Ranunculaceae)) dates back to Native Americans of the Cherokee and Iroquois tribes. Goldenseal was used externally for skin and eye infections and internally for relief from gastrointestinal symptoms. Today, goldenseal ranks among the 20 top-selling herbal products in the US.

In her group’s paper, Cech demonstrates the cooperative action in goldenseal between berberine, a weak, naturally-occurring antibacterial compound in the plant, and other chemicals that make the berberine more active. Even more fascinating is that these berberine-enhancing chemicals have no antibacterial activity on their own. In other words, these other chemicals potentiate the bacteria-killing effects of berberine. This potentiation is a form of synergy, a process where the combined action of two or more chemicals is greater than the sum of the parts.

(Disclosure: I have a NIH-funded collaboration with co-authors on Dr. Cech’s paper but not with her laboratory.)

Cech and her co-workers had already known that berberine killed Staphylococcus aureus bacteria at relatively high concentrations. Microbiologists use a term called, “minimum inhibitory concentration,” or MIC, to describe the minimum concentration of a drug required to kill a population of bacteria. But Cech had also observed that some parts of the goldenseal plant could increase the action of berberine.

To find out what these chemicals were, Cech’s lab purchased whole goldenseal plants, crushed them up in a series of alcohols and solvents, and separated out the constituents using a process called flash chromatography. Picture a tube filled with a specialized type of sand, silica gel. When you pour a gimmish on top of this column of separation material, some chemicals stick to it and flow through the bottom of the tube rather slowly while others wash past the silica quickly. Other chemicals bind somewhere in between, allowing this complex plant extract to be separated into smaller groups of chemicals.

Each fraction of these chemicals were then tested in multiple combinations alone and together with pure berberine. The research team observed that some of these fractions could increase the antibacterial action of berberine by a factor of 16. This synergistic action was not due to berberine in the plant extract of other related antibacterial alkaloid compounds.

After repeating the separation and antibacterial assay several times, Cech used a molecular sizing technique called mass spectrometry to identify two compounds whose size had not been previously known to occur in goldenseal. The group then used nuclear magnetic resonance spectroscopy to determine the strengths of bonds between individual atoms in the chemicals.

This combination of techniques led to the identification of three flavonoid compounds responsible for this synergy. One of the goldenseal chemicals is called sideroxylin. The other compound turned out to be two isomers that share the same molecular size, 8-desmethyl-sideroxylin and 6-desmethyl-sideroxylin. But how do these chemicals work?

Staphylococcus aureus has a protein that pumps toxic compounds out of the cell. This pump called NorA considers the plant chemical berberine to be toxic to its survival. The siderloxylin compounds block the action of the NorA pump and allow berberine to accumulate in the S. aureus cells to cytotoxic levels. Cech demonstrated that in S. aureus cells lacking the NorA pump, these chemicals could no longer potentiate berberine’s antibacterial action.

Cech’s team then went back to the original plant material to investigate where these synergistic compounds were present. Interestingly, the sideroxylin compounds were up to 50-fold more concentrated in the leaves relative to the root and rhizomes. In contrast, berberine was 5-fold more prevalent in the roots. Cech writes,

The finding that goldenseal leaf extracts have higher levels of synergists while root extracts contain higher levels of alkaloids suggests the potential benefit of using a mixture of root and leaf material in the production of dietary supplements from goldenseal. Further studies would, however, be needed to evaluate the safety and efficacy of goldenseal leaf extracts in vivo.

Indeed, goldenseal still needs to be studied in living models of bacterial infections rather than on laboratory dishes containing an optimal growth medium. Nevertheless, the traditional use of goldenseal alone has caused the plant to be endangered due to overharvesting in the wild. The plants used for this study were instead cultivated in their native environment of hardwood forest understory. Cech’s work provides a strong argument for herbalists and herbal compounds to be more responsible in sourcing their products and use cultivated plants.

But the primary significance of this work is that substantiation of common claims for combined or synergistic action in herbal products requires intensive chemical and biological investigation by a multidisciplinary research team. In this one case of goldenseal, synergy does indeed exist. This synergy-directed fractionation research strategy should be applied to other natural products where similar cooperative activity is suspected.


Junio HA, Sy-Cordero AA, Ettefagh KA, Burns JT, Micko KT, Graf TN, Richter SJ, Cannon RE, Oberlies NH, & Cech NB (2011). Synergy-Directed Fractionation of Botanical Medicines: A Case Study with Goldenseal (Hydrastis canadensis). Journal of Natural Products PMID: 21661731

Posted in: Basic Science, Herbs & Supplements

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