Zhang Jingli, Mohamad Fatin H, Wong Jia Hui, Mohamad Habsah, Ismail Abdul Hadi, Mohamed Yusoff Abdul Aziz, Osman Hasnah, Wong Kok Tong, Idris Zamzuri, Abdullah Jafri Malin
Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia.
Malays J Med Sci. 2018 Feb;25(1):101-113. doi: 10.21315/mjms2018.25.1.12. Epub 2018 Feb 28.
Bamboo shoot has been used as a treatment for epilepsy in traditional Chinese medicine for generations to treat neuronal disorders such as convulsive, dizziness and headaches. 4-hydroxybenzoic acid (4-hba) is a non-flavonoid phenol found abundantly in shoots (bamboo), fruits (strawberries and apples) and flowers. Kv1.4 is a rapidly inactivating -related member of the voltage-gated potassium channels with two inactivation mechanisms; the fast N-type and slow C-type. It plays vital roles in repolarisation, hyperpolarisation and signaling the restoration of resting membrane potential through the regulation of the movement of K across the cellular membrane.
Chemical compounds from bamboo shoots were purified and identified as major palmitic acids mixed with other minor fatty acids, palmitic acid, 4-hydroxybenzaldehyde, lauric acid, 4-hydroxybenzoic acid and cholest-4-ene-3-one. The response of synthetic 4-hydroxybenzoic acid was tested on Kv1.4 potassium channel which was injected into viable oocytes that was extracted from . The current were detected by the two-microelectrode voltage clamp, holding potential starting from -80 mV with 20 mV step-up until +80 mV. Readings of treatments with 0.1% DMSO, 4-hba concentrations and K channel blockers were taken at +60 mV. The ratio of tail/peak amplitude is the index of the activity of the Kv1.4 channels with ≥ 6 (number of oocytes tested). The decreases of the ratios of five different concentrations (1 μM, 10 μM, 100 μM, 1 mM and 2.5 mM) were compared with 0.1% DMSO as the control.
All concentration showed statistically significant results with < 0.05 except for 100 μM. The normalised current of the 4-hba concentrations were compared with potassium channel blockers (TEA and 4-AP) and all groups showed statistically significant results. This study also showed that time taken for each concentration to affect Kv1.4 does not play any significant roles.
4-hydroxybenzoic acid was found to be able to enhance the inactivation of Kv1.4 by lowering the membrane potential so that the abnormal neuronal firing can be inhibited. With IC50 slightly higher than 10 μM, increasing concentrations (100 μM, 1 mM and 2.5 mM) had shown to exhibit toxicity effects. The best concentration from this study is 10 μM with Hill slope of 0.1799.
竹笋在传统中医中历代被用于治疗癫痫，以治疗惊厥、头晕和头痛等神经紊乱。4-羟基苯甲酸（4-hba）是一种在竹笋、水果（草莓和苹果）及花朵中大量存在的非类黄酮酚。Kv1.4是电压门控钾通道中一种快速失活的相关成员，具有两种失活机制；快速N型和缓慢C型。它在复极化、超极化以及通过调节钾离子跨细胞膜的移动来指示静息膜电位的恢复过程中发挥着至关重要的作用。
从竹笋中纯化出的化合物被鉴定为主要是棕榈酸与其他少量脂肪酸、棕榈酸、4-羟基苯甲醛、月桂酸、4-羟基苯甲酸和胆甾-4-烯-3-酮的混合物。对合成的4-羟基苯甲酸在注射到从[具体来源]提取的有活力的卵母细胞中的Kv1.4钾通道上的反应进行了测试。通过双微电极电压钳检测电流，保持电位从-80 mV开始，以20 mV的步长上升至+80 mV。在+60 mV处读取0.1%二甲基亚砜、4-hba浓度和钾通道阻滞剂处理的读数。尾/峰幅度比是Kv1.4通道活性的指标，测试的卵母细胞数量≥6个。将五种不同浓度（1 μM、10 μM、100 μM、1 mM和2.5 mM）的比例下降与作为对照的0.1%二甲基亚砜进行比较。
除100 μM外，所有浓度均显示出具有统计学意义的结果（P<0.05）。将4-hba浓度的归一化电流与钾通道阻滞剂（TEA和4-AP）进行比较，所有组均显示出具有统计学意义的结果。该研究还表明，每种浓度影响Kv1.4所需的时间没有起到任何显著作用。
发现4-羟基苯甲酸能够通过降低膜电位来增强Kv1.4的失活，从而抑制异常的神经元放电。IC50略高于10 μM，浓度增加（100 μM、1 mM和2.5 mM）已显示出毒性作用。本研究中的最佳浓度为10 μM，希尔斜率为0.1799。
