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- Ashwagandha (Withania somnifera, Solanaceae)
- Anticancer Activities
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Date:
10-15-2015 | HC# 051541-530
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Re: Review of Anticancer Activities of Ashwagandha
Rai M, Jogee PS, Agarkar G, Alves dos Santos
C. Anticancer activities of Withania
somnifera: current research, formulations, and future perspectives. Pharm Biol. April 7, 2015; [epub ahead
of print]. doi: 10.3109/13880209.2015.1027778.
Of the Withania genus' 26 species, ashwagandha
(Withania somnifera, Solanaceae),
indigenous to dry regions of India, Pakistan, Afghanistan, Africa, and the
Mediterranean and cultivated in the US, is the best known and most studied. The
evergreen shrub flowers nearly all year, with small fleshy fruits conferring
another common name, "winter cherry." Metabolic profiling of a crude
extract of ashwagandha leaves and roots found 62 primary and secondary
metabolites in leaves and 48 in roots; 29 were common to both, including fatty,
organic, and amino acids; sugars; flavones; and sterols. Several ashwagandha
chemotypes are grown for medicinal use in India. The authors review potential
anticancer uses of ashwagandha's parts and extracts, compounds isolated from
ashwagandha, and ashwagandha formulations. The abstract states that a search of
the literature was conducted in scientific databases and via library search;
this is not further discussed.
Ashwagandha extracts
show significant anticancer activity through several pathways. Mechanisms of
action may include changes in levels of endogenous peroxide dismutase,
catalase, and ascorbic acid, and reduced lipids. Antitumor effects may also include
increasing the sensitivity of cancer cells to conventional chemotherapeutic drugs
and reducing their adverse effects without impeding their efficacy. Ashwagandha
may help repair oxidative damage caused by tumor cells and reduce inflammation.
Epigenetic changes, critical in cancer etiology, may be reversed by some
ashwagandha compounds, including withaferin A (WA). WA occurs at higher levels
in chloroform extracts of ashwagandha leaves and bark than in stem and root
extracts. An aqueous leaf extract had anticancer effects, with triethylene
glycol (TEG), an activator of p53 and pRB (tumor suppressor protein), identified
as the active component. A hydroalcoholic leaf extract was more potent against
breast than ovary or lung cancer cells. A methanolic leaf extract with WA,
withanoside IV, and withanoside VI induced neurite outgrowths in neuroblastomas.
Ethanol, alcohol, and
other extracts of ashwagandha roots have been found effective against breast
cancer in vitro and in vivo, with reduced cancer cell division and tumor growth.
An ethanolic root extract, tested with the conventional anticancer agent
doxorubicin, found the former sparing of healthy cells but cytotoxic to breast
cancer cells; the latter, cytotoxic to both. In patients with breast cancer undergoing
chemotherapy, a root extract aided recovery from cancer fatigue and improved
quality of life. A root extract has been reported to be effective against
cervical cancer. A cumulative review of methanol, aqueous, chloroform, n-butanol, ethyl acetate, and n-hexane root extracts identified anticancer
compounds in each, with alkaloids, flavonoids, steroids, and terpenoids most
significant.
Withanolides and
withaferins, steroidal lactones specific to ashwagandha, are of interest for many
potential benefits. Withasomniferin-A and 5-dehydroxy withanolide-R from aerial
plant parts have been studied for immunomodulatory effects. For anticancer
activity, WA, ashwagandha's main constituent, is considered most important and
potent. WA reduced transplanted tumor cell growth in mice and both reduced
metastasis and prevented chemically induced as well as oncogenic cancers in
rodents. While there are many reports of WA's anticancer effects, its exact
mechanism is unknown. WA is target-specific, showing "remarkable"
reduction of protein β-tubulin, integral to microtubules. Its specificity
extends to mitogen-activated kinases, where it induced breast cancer cell
apoptosis. One study found WA's efficacy against breast cancer based on
inhibition of epithelial-mesenchymal transition and decreased vimentin protein
expression; another study found that Notch signaling, overexpressed in breast
cancer cells, was decreased by WA, with reduced Notch1 cleavage.
Hyperthermia,
sometimes used with radiology, can induce cancer cell apoptosis but is not an
efficient anticancer treatment alone. Hyperthermia can be enhanced with WA; one
study found that neither treatment alone was as effective as the combination in
promoting apoptosis. WA can regulate dysfunctional and irregular cell cycles at
the G2/M phase, inhibiting prostate and some other cancers. Fed to hens,
ashwagandha root powder increased their stromal and intratumoral natural killer
(NK) cells compared to unsupplemented hens, who had only their stromal NK cells
increased.
Among withanolides
studied for anticancer effects, withanolide D (witha-D) caused apoptosis in
pancreatic cancer cells. A comparative study of 36 WA analogs found that a
modified withanolide scaffold could enhance heat-shock-inducing activity (HSA)
and might be used to design a novel drug product that would stimulate cellular
defenses. A new withanolide, 5,6-de-epoxy-5-en-7-one-17-hydroxy WA, discovered
in ashwagandha roots and leaves, has been found more effective against liver
and breast cancers than colon and prostate cancers. Withanone (WN), tested alongside
WA in many studies mentioned here and found less potent in its anticancer
effects, is reported to reduce survivin expression, binding to its active
domain and impeding its inhibition of apoptosis. A standardized ashwagandha
formula, identified only as "WSF," has been reported to exert
anticancer and immunomodulatory effects in vitro and in vivo and is considered
a potentially valuable cancer chemotherapy adjunct.
Unfortunately, this complex report on an important
subject is rather poorly organized, making it difficult to find all information
included about, for example, WA. No studies are described in any detail, nor is
their quality assessed. The article might have benefited from copy editing, as
it suffers from numerous incomplete sentences and misused or missing words.
—Mariann Garner-Wizard
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