This past Saturday, we took a three-hour bus ride from Paris to the Loire Valley to visit two famous chateaus: the Château de Villandry and the Château de Chenonceau. Château de Villandry especially caught my attention because despite its rather plain exterior compared to other chateaus. It has one of the most beautifully designed gardens. Château de Villandry have a long history since the 14th century, but most recently, Joachim Carvallo, a Spanish doctor and researcher, bought the property in 1906. As we stood on the upper levels of the chateau, I was amazed by the geometric designs of the decorative gardens that represented tender, passionate, fickle, and tragic love. Carvallo renovated the château and designed medicinal gardens to further his research. In addition to the medicinal herb garden, there are also flower gardens, vegetable gardens, and waters gardens, which are representative of renaissance style chateaus.
The medicinal herb garden is farther away from the main building because it was built in the 1970s by Carvallo’s grandson according to his original design. The garden contains various different types of herbs, roots, and leaves that have therapeutic properties. As I was meandering through the garden slowly, a slight scent of minty lemon caught my attention. The scent originated from a little bush with green leaves that resembled the shape of mint leaves. A little web browsing showed that the plant is called lemon balm, or Melissa officinalis. Lemon balm is usually used to make herbal tea, which I don’t particularly like. However, since Carvallo chose to have lemon balm planted in his herb garden, I am curious to find out the beneficial effects of this nice smelling plant.
Lemon balm has various therapeutic properties ranging from lowering anxiety to treating Alzheimer’s disease (Maguire et al.). Lemon balm has such a wide variety of therapeutic uses because of its effects in many neurotransmitters that are important for neuron communication in the body. Neurotransmitters are molecules secreted by one neuron to another for signaling purposes; most of them can be divided into two categories. One group of neurotransmitters will increase the activity and electrical firing of the recipient neuron. The other group of neurotransmitters will decrease the activity and electrical firing in the neuron receiving the molecules.
Among many studies investigating possible usages of lemon balm for treating different diseases, a study on lemon balm extract’s ability to induce neurogenesis in dentate gyrus of hippocampus, an area of the brain that is responsible for forming new memories, seems particularly promising for treating many memory related diseases such as Alzheimer’s (Yoo et al., 2011). Neurogenesis in the dentate gyrus focuses on the formation of granule cells, a cell type that is thought to be responsible for spatial memories (Colicos and Dash, 1996). The process of neurogenesis starts with the proliferation of granule cell progenitors in the subgranular zone, which then migrate to the granule cell layer where the new granule neuronal cells are made (Yoo et al., 2011).
To see if lemon balm actually promotes neurogenesis, Yoo et al. set up three groups of mice. The first group was fed with 50mg/kg lemon balm extract, the second group received a higher dose of 200mg/kg, and the last group is a control group in which the mice were fed with distilled water (Yoo et al., 2011). All three groups were fed once a day for 21 days. To track the effect of lemon balm on neurogenesis in the dentate gyrus, we have to monitor several proteins that are produced as by-products of neurogenesis. Ki-67 is a protein that will be present in the cellular nucleus during cell proliferation. DCX, another protein, is expressed in immature neurons, which is indicative of new neuron formation. To see if these proteins are made in the dentate gyrus, antibodies that will attach themselves specifically to these two proteins were used. To quantify how many antibodies are attached to these two proteins, a stain was performed on sections of the dentate gyrus after the antibodies were administered (Yoo et al., 2011).
The results of this study is astonishing in which there is a 7-fold increase in the level of Ki-67 in the mice group that received 200mg/kg lemon balm compared to the control group that received water. Similarly, there is also significant increase in the level of neurons expressing DCX in the dentate gyrus for the two experimental groups that received lemon balm extract (Yoo et al., 2011). The combined increases in expression of these two proteins indicate that neurogenesis of granule cells are increased due to the intake of lemon balm extract by the mice.
Although there are still many differences between mice and human, I think it wouldn’t hurt to drink some lemon balm tea once in a while. If granule cell neurogenesis can be induced by lemon balm extract as suggested by the mouse model, drinking some lemon balm tea might actually improve my spatial memory and help me navigate through the complex RER and metro system in Paris!
Colicos MA, Dash PK (1996) Apoptotic morphology of dentate gyrus granule cells following experimental cortical impact injury in rats: possible role in spatial memory deficits. Brain Research 739:120-131.
Maguire MA, Dvorkin L, Whelan J Boston Healing Landscape Project – Melissa Officinalis. In. Boston University School of Medicine.
Yoo DY, Choi JH, Kim W, Yoo KY, Lee CH, Yoon YS, Won MH, Hwang IK (2011) Effects of Melissa officinalis L. (lemon balm) extract on neurogenesis associated with serum corticosterone and GABA in the mouse dentate gyrus. Neurochemical research 36:250-257.