Evaluation of Natural and Botanical Medicines for Activity against Growing and Non-growing Forms ofB. burgdorferi

Abstract

AbstractLyme disease is the most common vector-borne disease in the US. Although the current recommended Lyme antibiotic treatment can cure the majority of Lyme disease patients, about 10-20% patients continue to suffer from persisting symptoms. There have been various anecdotal reports on the use of herbal extracts for treating patients with persisting symptoms with varying degree of improvements. However, it is unclear whether the effect of the herb products is due to their direct antimicrobial activity or their effect on host immune system. In the present study, we investigated the antimicrobial effects of 12 commonly used botanical medicines and 3 other natural antimicrobial agents for potential anti-Borrelia burgdorferiactivity in vitro. Primary criteria for selecting compounds for the present study included agents that had shown significant anti-borrelial effects in previous studies, have favorable safety profiles, and can be absorbed systemically. Among them, 9 natural product extracts at 1% were found to have good activity against the stationary phaseB. burgdorfericulture compared to the control antibiotics doxycycline and cefuroxime. These active herbs includeCryptolepis sanguinolenta, Juglans nigra(Black walnut),Polygonum cuspidatum(Japanese knotweed),Artemesia annua(Sweet wormwood),Uncaria tomentosa(Cat’s claw),Cistus incanus, andScutellaria baicalensis(Chinese skullcap). In contrast,Stevia rebaudiana, Andrographis paniculata, Grapefruit seed extract, colloidal silver, monolaurin, and antimicrobial peptide LL37 had little or no activity against stationary phaseB. burgdorferi. The minimum inhibitory concentration (MIC) values ofArtemesia annua, Juglans nigra, andUncaria tomentosawere quite high for growingB. burgdorferi, despite their strong activity against the non-growing stationary phaseB. burgdorfericells. On the other hand, the top two active herbs,Cryptolepis sanguinolentaandPolygonum cuspidatum, showed strong activity against both growingB. burgdorferi(MIC=0.03%-0.06% and 0.25%-0.5% respectively) and non-growing stationary phaseB. burgdorferi. In subculture studies, only 1%Cryptolepis sanguinolentaextract caused complete eradication, while current Lyme antibiotics doxycycline and cefuroxime and other active herbs includingPolygonum cuspidatum, Artemesia annua, Juglans nigraandUncaria tomentosacould not eradicateB. burgdorferistationary phase cells as many spirochetes were visible after 21-day subculture. Further studies are needed to identify the active ingredients of the effective herbs and evaluate their combinations for more effective eradication ofB. burgdorferiin vitro and in vivo. The implications of these findings for more effective treatment of persistent Lyme disease are discussed.