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The present study was undertaken to evaluate the effects of ultra low concentrations (10-9 or 10-14 M) of morphine on neurite elongation in cultured neurons dissociated from rat spinal cords and cerebral cortex. In fetal serum (FS) or fetal serum-free supplemented with cAMP media, the length of longest neurite was significantly increased by 10-9 or 10-14 M morphine. For example, 10-14 M morphine increased neurite length by 24±0.5% and 27±0.3% in spinal cord neurons, and 18±0.2% and 17±0.6% in cortical neurons. Morphine (10-6 M) had no significant effect on neurite length of spinal and cortical neurons. The relative frequency distribution of neurite length revealed 61±2.7% of spinal neurons and 48±2.6% of cortical neurons are responsive to ultra low concentrations of morphine. In the responsive populations, morphine (10 -14 M) enhanced the neurite outgrowth in spinal neurons by 58±0.9% and 48±1.2% and in cortical neurons by 31±0.6% and 28±0.9% in FS and cAMP-supplemented media, respectively. Pretreatment with naloxone did not prevent the morphine effect. The result shows that morphine at ultra low concentrations enhances neurite outgrowth of spinal and cortical neurons via a naloxone-independent mechanism.

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Merrilactone A (1) was isolated in only 0.004% yield from the methanol extracts of the pericarps of Illicium merrillianum. Structural elucidation of Merrilactone A revealed a compact, cage-like pentacyclic architecture of high molecular complexity, featuring seven stereocentres, five of which as contiguous fully substituted carbon atoms, two γ-lactones and a central oxetane ring. Merrilactone A also exhibits an important neurotrophic activity, significantly promoting neurite outgrowth in the primary cultures of foetal rat cortical neurons at very low concentrations. Structurally, merrilactone A is related to anislactones A and B, a pair of epimeric sesquiterpene dilactones discovered ten years earlier by Kouno and co-workers from the related Illicium anisatum plant. Fukuyama has shown that anislactone B can be converted into merrilactone A using a simple three step sequence, suggesting that the anislactones may be biogenetic precursors to merrilactone A. Described in this thesis are our research efforts directed towards developing a conceptually novel synthetic route enabling regiodivergent total synthesis of both anislactone A / B and merrilactone A. Our synthetic route (around 22 steps) features several key reactions, which include a [2+2] photo-cycloaddition reaction, Tiffeneau-Demjanov ring expansion and titanium(III) mediated radical cyclization.